According to one embodiment, a head stack assembly incorporating device connects a head stack assembly to the base of a magnetic disk device by screwing a connector on the bottom surface of the rotational shaft of the head stack assembly and a connector on the base of the magnetic device together. The head stack assembly incorporating device includes a chuck and a driving-force transmitter. The chuck pinches the rotational shaft of the head stack assembly from the upper surface of the head stack assembly to be fixed to the rotational shaft. The chuck is rotatable around the central axis of the rotational shaft. The driving-force transmitter transmits a rotational force to the chuck.