To provide an opening part device for firmly installing a lock member on a stile having a small face width, by preventing run-out of the lock member when opening and closing a door body.

This opening part device has the lock member 11 on the door end of the door body connected to a frame body by a hinge; and is characterized in that this lock member 11 has a box lock 21 and a pair of pedestals 25 and 26 for receiving grips 23 and 24 for operating this box lock 21, and a reinforcing member 45 is installed on a door end side stile 5 of the door body, and this reinforcing member 45 and the door end side stile 5 are fixed by being nipped by the pair of pedestals 25 and 26.