There is provided an inertial drive actuator in which, a small-sizing is easy, including a first displacement generating mechanism of which, one end is adjacent to a fixed member, and a first displacement is generated in the other end thereof, a second displacement generating mechanism of which, one end is adjacent to the fixed member, and which generates a second displacement in the other end thereof, a driving mechanism which applies a voltage for displacing the first displacement generating mechanism and the second displacement generating mechanism, a vibration substrate which is connected to the other end of the first displacement generating mechanism and the other end of the second displacement generating mechanism, and which is displaceable in a plane in which, there exist a direction of the first displacement and a direction of the second displacement, a mobile object which is disposed to be facing the vibration substrate, and which moves with respect to the vibration substrate by an inertia with respect to a displacement of the vibration substrate, and a friction controlling mechanism which changes a frictional force between the mobile object and the vibration substrate.