This study aims to review the policy responses of the European Central Bank (ECB) during the global economic crisis and subsequent Euro crisis, and sheds light on the logic and backgrounds related to these responses. The ECB used increasingly non-conventional measures, such as the purchase of sovereign bonds, which was unexpected before the crisis. In this context, the study raises the following question: is the increasing use of non-conventional measures temporary one in response to an unprecedent crisis or is it a sign of structural change in ECB’s role?    
The ECB has features in common with most of central banks of advanced countries, but it differs from them in three aspects. First, the ECB has a mandate only with respect to price stability. It has a very high level of institutional and political independence. Third, the ECB and the national central banks of the Eurosystem are forbidden to finance governments (monetization). These salient features of the ECB are very similar to those of the German Bundesbank. Given the role of Deutsche Mark and the Bundesbank in the European monetary integration, it seems that the ECB would include features that are legacies of the Bundesbank.     
As the Euro crisis spread over the entire eurozone starting from the European peripheries, responses by the ECB have been increasingly active. In order to keep financial markets stable, it has intervened with non-conventional measures. For the first time, it made large-scale purchase of sovereign bonds from the secondary market and provided long term liquidity to financial institutions with low interest rates. In addition, its Governing Council declared the outright monetary transaction (OMT), which means that the ECB will purchase unlimited quantity of sovereign bonds in case of a crisis. Its willingness and determination toward market intervention played an important role in mitigating the crisis. However, these measures, particularly the purchases or plans to purchase sovereign bonds, caused a dispute between different actors and principles. They were conceived and implemented amidst tension between member states, particularly Germany and France and between ECB’s mandate (price stability) and financial stability (response to the euro crisis).   
During the crisis, the ECB made it clear that its priority and mandate are in maintaining price stability and emphasized that non-conventional measures were implemented to secure a ‘transmission channel’ of monetary policy. Eventually its measures contributed to mitigation of tensions in the sovereign market, but it emphasized repeatedly that these measures were conducted as a part of its monetary policy. Besides, its president underlined that the ECB excluded completely all political influences in its policy consideration.  
Regarding the future change in ECB’s role, it is necessary to note and consider three aspects. First, the Euro crisis provided occasions for reflecting upon the role of the central bank as the ‘lender of last resort’. As the crisis deepened, the role of ECB has been up for discussion. This means that all debates regarding its role during the crisis could become a starting point for its institutional change, albeit small. Second, the role of the ECB will be impacted significantly by the level of economic integration in the EU. Considering that the EU does not have any authority to impose taxes and conduct fiscal policy, it is hardly expected that the ECB provides credit to any European institutions and governments. Third, the ECB has now a supervisory authority over the commercial banks in Eurozone under the ongoing banking union. This means that the ECB has to follow two simultaneous objectives, price stability and financial stability. While the ECB declared that two objectives will be treated individually according to the ‘principle of separation,’ the political and economic dynamics that the ECB has to encounter will be more complicated than before.