PURPOSE: To provide a cheap mounting device which can be mounted and removed easily, by forming resilient at least either of the breaker side pawls and also at least either of the DIN rail side pawls.

CONSTITUTION: Two breaker side pawls 7a, 7b for installing a circuit breaker at the two ends are molded with plastic in a single piece, and at least either of these pawls 7a, 7b is made resilient to enable easy mounting and removal, and a knob 7d is furnished for a person to easily catch it by hand at the time of dismantling. Two rail side pawls 7e, 7f for mounting DIN rail 6 are provided in the center of the opposite side to the breaker side pawls 7a, 7b, and at least either of these rail side pawls 7e, 7f is made resilient. This accomplishes a cheap mounting device (adapter) for DIN rail with which mounting and removal can be made efffectively.