The optical image stabilizer shifts an image stabilizing element with respect to an optical axis of an optical system to reduce image shake. The stabilizer includes a lock ring which is rotatable to a lock position to limit shift of the image stabilizing element and to a lock-releasing position to allow the shift of the image stabilizing element, an actuator which rotates the lock ring to the lock position and the lock-releasing position, and a biasing mechanism which mechanically biases the lock ring rotated to the lock position toward the lock position and biases the lock ring rotated to the lock-releasing position toward the lock-releasing position.