To increase the attachment space of a board attachment tool to a small door.

At a control center, a unit frame body 6 holding a control unit 5 is put into a unit room of a frame body and a cut window is provided on an open/close door which covers the unit room of the frame body. Then a small door 7 where a board attachment tool 9 of the unit 5 is attached is provided on the front face of the frame body 6 in a freely opening/closing way, and also the door 7 touches the cut window of the open/close door. In such a constitution, a vertical cut groove 6d is formed in the front of a side plate 6c of the frame body 6 together with a bent piece 6e prepared at a vertical end of the groove 6d. A vertical end of the bent part of the door 7 is bent again at the side of the plate 6c as a bent piece 7b which is movably fit into the piece 6e of the frame body 6. Accordingly, no hinge is required to be attached to the door 7 and the attachment space is increased for the tool 9 of the door 7.