The main purpose of this study is to identify the causes of Catalonia’s independence movement. Established researches suggest some reasons of Catalonia’s independence movement: 1)economic crisis and discontents, 2)national identities and cultural uniqueness and 3)politics of recognition. However, this study argues that Spanish institutions, particularly political institutions established during the democratization process, are the most important cause to propel Catalonia’s independence movement. Spanish democratization process was characterized as ‘pacted’ or ‘transformation’ democratization because Spanish people tried to evade confrontations and conflicts due to harsh civil war and dictatorship. In the same vein, Spanish democratization established unique political institutions for assuring political stability. Both unequal and unfinished decentralization scheme and particular electoral system not only strengthened regional politics and regional political parties, but also led to Catalonia’s independence movement.