PURPOSE: To easily obtain a proper positional relationship between a head carriage and a holder in the magnetic disk device having a function for vertically moving a head arm of the head carriage arranged with a magnetic head.

CONSTITUTION: Contact parts 31a and 31b of a frame 31 are formed in the vicinity of tip parts 22a and 22b of the holder for vertically moving a movable arm 13. A protection member 25 is freely slidably supported by a top plate 21a, and arm parts 25a and 25b are extended from sliding contact parts 30a and 30b in sliding contact with the lower surfaces of the tip parts 22a and 22b of the holder. At the time of positioning the movable arm 13 in a position of inserting or ejecting a disk cartridge 18 by the tip parts 22a and 22b of the holder 21, the arm parts 25a and 25b of the protection member 25 are moved into a position to be contact with the upper surfaces of the contact parts 31a and 31b of the frame, so that displacement of the tip parts 22a and 22b of the holder is regulated.