To provide a power conversion mechanism capable of using nonlinearity of a cam mechanism, while miniaturizing the mechanism, in the mechanism for providing mechanical output by a difference in an input system between two systems.

This power conversion mechanism has a screw member having a screw groove, a first input system for rotating this screw member, a nut member screw-fitting with the screw groove and a second input system for rotating this nut member, and has an operation conversion part using screw-fitting advancing-retreating displacement of the nut member.