Abstract: In an electric actuator, an output shaft has a housing recess. An end of a motor shaft is housed in the housing recess. A first bearing supports the motor shaft in the housing recess. The motor shaft has an eccentric shaft. A deceleration mechanism includes an external gear connected to the eccentric shaft via a second bearing, an internal gear engaged with the external gear, a flange part expanding from the output shaft, and protrusions protruding from the flange part and disposed along the circumferential direction. The external gear has holes recessed on the other side in the axial direction. The holes are disposed along the circumferential direction and each have an inner diameter larger than the outer diameter of the protrusion. The protrusions are inserted into the holes respectively and support the external gear to be swingable around the central axis via the inner surfaces of the holes.