To install a push-button group unit on a cabinet, without making significant structural changes on an existing cabinet and the push-button group unit, and without the use of a welding means.

The push-button group unit 10 having a coupling bar 11 is installed on a cabinet 30 with an axis part on the cabinet 30 side inserted into a projection with a hole 12 on the coupling bar 11 side. The coupling bar 11 is pushed onto the cabinet 30 by a wiring board 50, and the coupling bar 11 is supported by an end face 41, in the length direction of a support member 40 of a rib shape provided in the cabinet 30. The support members 40 are arranged in the mutual spacing 16 of the mutually adjoining push buttons 13 of the push-button group unit 10.