PURPOSE: To facilitate automatic change of a punch by moving the punch horizontally up to an upper position of a mounting hole formed in an upper turret, then lowering the punch, and detecting whether a lower end part of the punch comes into contact with a wall face of the mounting hole during lowering or not to control the lowering operation.

CONSTITUTION: When a punch of turret punch press is changed, a punch P for change is gripped by a punch change device, and this punch P is horizontally moved up to an upper position of a mounting hole 91 formed in an upper turret 15a. Next, the punch P is lowered to detect whether a lower end part of the punch comes into contact with a wall face of the mounting hole 91 during lowering process or not. When its contact with the wall face is detected, a height position of the lower end part is measured, and the measured height is compared with a reference height position. When the detected height position is lower than the reference height position, the punch P for change is lowered furthermore. Moreover, if the lower end part of the punch comes into contact with an upper face of the upper turret 15a while the punch is lowered, a central position of the mounting hole 91 is searched by a fuzzy search method to move the punch P horizontally.