To provide an extremely simple and small-sized electric actuator capable of supplying a precise signal for the angle position of a drive shaft with high reliability, and a bicycle transmission equipped with it.

This electric actuator for controlling a bicycle part such as bicycle front wheel or rear wheel transmission or the like comprises an electric motor 2 including an output shaft 3, the drive shaft 11 rotatably mounted within the casing 10 of an actuator 1 and connected to the output shaft 3 of the electric motor 2 through a reduction gear 9, and an angle position sensor 25 for the drive shaft 11. The angle position sensor 26 is a rotation potentiometer related to the drive shaft 11 provided within the casing 10 of the actuator 1.