To automate an attaching/detaching operation for a pin for forming a through hole in a concrete molded product, and an opening/closing operation for a movable form.

A form 1 is arranged in a manner liftable by a lifting, device 14. The pin 7 fixed to a base member 8 is made to protrude and retract from and into a through hole 17 of a stationary mold 2 by going up and down of the form 1. Left and right movable molds 3 and 4 are separated from the stationary mold 2 by engagement of a guide pin 23 and a guide groove 22 owing to rise of the form 1, and abut against the stationary mold 2 by descent of the form 1. Thereby, an attaching/detaching operation for the pin 7 for forming the through hole 17 in an arch-shaped block 5 and an opening/closing operation for respective movable molds 3 and 4 are automated.