The European Union presents itself as the most successful supranational experiment. In view of its inevitable and necessary regional integration project, the present research aims to verify the existence of a democratic deficit in its parliamentary institution. To this end, liberal democratic theories that give theoretical form to western representative democracy will be addressed, so that the institutions that make up the bloc can be founded. Afterwards, the positions regarding the existence of the democratic deficit in the Union, the perspective of a constitutionalism beyond the Nation-State, the impossibility of federalist deepening, and the criticisms of the liberal Europeanist approach will be analyzed, so that the performance of Parliament can be analyzed. European Union as a democratically legitimate supranational representative body.