The present invention provides an actuator, an optical device, and a projector. The actuator can inhibit the vibration out of the in-plane direction to achieve expected motion, and the optical deviceand the projector have the actuator. At least one of a first beam portion (11) and second beam portions (12a, 12b) is provided with an out-of-plane vibration suppressing structure configured to suppress vibration of a movable portion (10) in an out-of-plane direction vertical to an in-plane direction. Thus, unintentional occurrence of unintentional movement in the out-of-plane direction vertical to the in-plane direction can be suppressed. Furthermore, in this case, a size reduction of a device can be achieved in comparison with a case where a device includes a motor disposed for rotation driving, for example.