A mold pin (14, 34, 46, 60) for forming a spike pin mounting hole in a tread surface of a tire, the mold pin (14, 34, 46, 60) comprising: a mounted portion (16, 36, 48) which is a portion to be inserted into a mold and fixed; and a pin hole formation portion (18, 38, 50, 62) which is a portion to be buried in the tire to form a spike pin hole, wherein the pin hole formation portion (18, 38, 50, 62) includes an expanded portion (26, 40) formed at or near a tip end thereof, and the expanded portion (26, 40) is configured to be displaceable relative to the mounted portion (16, 36, 48) in a central axis direction of the pin hole formation portion (18, 38, 50, 62), wherein the mounted portion (36, 48) includes: a guide space formed so as to be coaxial with the pin hole formation portion (38, 50); and an engaging portion (44, 54) formed within the guide space, the pin hole formation portion (38, 50) includes a to-be-engaged portion (42, 52) formed at a base end thereof, displacement of the pin hole formation portion (38, 50) in the central axis direction is guided by the guide space, and separation of the pin hole formation portion (38, 50) from the guide space is prevented by the to-be-engaged portion (42, 52) being engaged with the engaging portion (44, 54) or wherein the pin hole formation portion (18, 62) includes: a base portion (22, 64) fixed to the mounted portion; and an extensible portion (24, 66) displaceable in a central axis direction of the base portion (22, 64), the expanded portion (26, 40) is formed at or near a tip end of the extensible portion (24, 66), the base portion (22, 64) includes a coaxial guide space and an engaging portion (30, 64c) formed within the guide space, the extensible portion (24, 66) includes a to-be-engaged portion (28, 70) formed at a base end thereof, displacement of the extensible portion (24, 66) in the central axis direction of the base portion (22, 64) is guided by the guide space, and separation of the extensible portion (24, 66) from the guide space is prevented by the to-be-engaged portion (28, 70) being engaged with the engaging portion (30, 64c). a mounted portion (16, 36, 48) which is a portion to be inserted into a mold and fixed; and a pin hole formation portion (18, 38, 50, 62) which is a portion to be buried in the tire to form a spike pin hole, wherein the pin hole formation portion (18, 38, 50, 62) includes an expanded portion (26, 40) formed at or near a tip end thereof, and the expanded portion (26, 40) is configured to be displaceable relative to the mounted portion (16, 36, 48) in a central axis direction of the pin hole formation portion (18, 38, 50, 62), wherein the mounted portion (36, 48) includes: a guide space formed so as to be coaxial with the pin hole formation portion (38, 50); and an engaging portion (44, 54) formed within the guide space, the pin hole formation portion (38, 50) includes a to-be-engaged portion (42, 52) formed at a base end thereof, displacement of the pin hole formation portion (38, 50) in the central axis direction is guided by the guide space, and separation of the pin hole formation portion (38, 50) from the guide space is prevented by the to-be-engaged portion (42, 52) being engaged with the engaging portion (44, 54) or wherein the pin hole formation portion (18, 62) includes: a base portion (22, 64) fixed to the mounted portion; and an extensible portion (24, 66) displaceable in a central axis direction of the base portion (22, 64), the expanded portion (26, 40) is formed at or near a tip end of the extensible portion (24, 66), the base portion (22, 64) includes a coaxial guide space and an engaging portion (30, 64c) formed within the guide space, the extensible portion (24, 66) includes a to-be-engaged portion (28, 70) formed at a base end thereof, displacement of the extensible portion (24, 66) in the central axis direction of the base portion (22, 64) is guided by the guide space, and separation of the extensible portion (24, 66) from the guide space is prevented by the to-be-engaged portion (28, 70) being engaged with the engaging portion (30, 64c).