A rebounding phenomenon of an actuator assembly is to be prevented and device assembling work and maintenance work are to be carried out separately from stopper removing work. In one embodiment, a magnetic disk device includes a stopper 50 for restricting a turning range of an actuator assembly 8 having a coil support 22 in a magnetic disk device. In the stopper 50, rubber 51 is cantilevered by a support rod 261 so as to undergo a moment of force and fulfill a shock absorbing function in order to restrict an excessive movement of the actuator assembly 8 to an inner or an outer side when the rubber 51 is abutted against a first arm 22a or a second arm 22b of a bifurcated shape of the coil support 22, the support rod 261 is disposed outside a turning track of turning ends of the first and second arms 22a, 22b of the coil support 22, and a permanent magnet 52 is embedded in the rubber 51 to attract the first and second arms 22a, 22b.