To provide a "disk drive" which can suppress the occurrence of backlash in a power transmission mechanism, can suppress variation of feeding load of a head, and can stably perform feeding control of the head without complicating the structure of power transmission mechanism to the head.

If a head base 21 and a rack member 31 move in an 1 direction, a ratio (Rb/Ra) of pitch circle diameter in a meshing part of biasing rotational body 52 and a driven rotational body 54 on which pull force Fp of a pull coil spring acts becomes small, transmissibility of torque falls off, and the excessive biasing force Fx can be prevented from acting on the rack member 31. As a result, moderate biasing force Fx can be stably given to the rack member 31, and the backlash can be suppressed.