Provided is an actuator device used in a plurality of sites of a multi-shaft driving mechanism such as a multi-shaft manipulator, a robot arm, a leg structure and a snake-shaped robot. A torque sensor is connected to a bearing such as a cross roller bearing through a mount part. The torque sensor is driven by an outer ring relative to a stationary part case of an actuator device. An attachment surface of an output shaft frame is arranged in a position offset from the bearing on a side of the stationary part case. An entire length of the actuator device in an output shaft direction does not change also after the output shaft frame is attached and an occupied space does not increase.