A method can be used for manufacturing an ethylene-propylene-diene terpolymer for a fuel cell. A polymerization step includes subjecting an organic chelate compound forming a coordinate bond, a vanadium-based Ziegler-Natta catalyst, an organoaluminum compound, and ethylene, propylene, and diene monomers, together with a solvent, to polymerization in a reactor. A separation step includes recovering residual catalysts and unreacted monomers from the stream discharged from the reactor. An acquisition step includes recovering the solvent from the stream deprived of the residual catalysts and unreacted monomers to acquire the ethylene-propylene-diene terpolymer.