To provide a mounting method of a guide pin for a disk brake device which does not fracture a calking part during caulking and keeps the verticality precision of the guide pin high.

The mounting method of the guide pin is employed for a floating type disk brake device. The guide pin 30 includes a sliding part 32 held in a sliding hole, a base end part 34 press-fitted into a through hole 26 formed in a support 22, and a flange part 36 arranged between the sliding part 32 and the base end part 34. A V-shaped cross-sectional recess 40 is formed at the tip of the base end part 34. The base end part 34 is press-fitted into the through hole 26 with a press fitting jig 60. A calking jig 62 having a protrusion 62a which has a tip acuter than the V-shaped with a rounded edge is pressed against the tip of the base end part 34 pressed through and protruded. A calking part 38 is formed by extending outwardly a wall part 40b constituting the recess 40. The method is characterized by clamping the support 22 forming the through hole 26 between the flange part 36 and the calking part 38.