An electric actuator includes a motor including a rotor having a motor shaft extending along a central axis and a stator, a deceleration mechanism connected to the motor shaft, an output shaft, a bearing, and a deceleration mechanism case. The motor shaft includes an eccentric axis part with an eccentric axis as a center. The bearing is fitted on of the eccentric axis part. The deceleration mechanism includes an internal gear in a ring shape; an external gear connected to the eccentric axis part via the bearing and engaging with the internal gear; and an output flange part which transmits rotation of the external gear around the central axis to the output shaft. The deceleration mechanism case includes a plurality of gear supporting parts which support an end surface of the internal gear facing one axial-direction side and which are disposed in a circumferential direction with intervals from one another.