A mechanism is provided for restraining and releasing an actuator suspension assembly in a magnetic disk device which is in a retracted position. In a magnetic disk device, according to one embodiment, a magnetic disk 4a is formed of an electrically conductive material and there is disposed a latch member 50 which holds an eddy-current magnet at one end thereof and is provided with a latching portion at an opposite end thereof. An actuator suspension assembly 8 lies in a retracted position and is restrained at a frame engaging portion 23 thereof by means of the latch member. The eddy current magnet is disposed in such a manner that a magnetic pole thereof is opposed to a surface of the magnetic disk at a position close to the disk surface. When the magnetic disk is rotated, an eddy-current is generated and a force is exerted on the eddy-current magnet, so that the latch member turns and releases the actuator suspension assembly.