To provide a circuit device by which a removal preventing tool is prevented from being pivoted downward from an inlet portion in a state that no plug is inserted in the inlet portion to always push a cord connecting side of the plug from above by the removal preventing tool, thereby surely inhibiting a state that the plug is carelessly pulled out.

The circuit device is composed of a pair of supporting members 1 located on both side of a plug P inserted in an inlet portion Q and the removal preventing tool 11 for the plug P pivotally installed in a pair of the supporting members 1, and stopper members 3 are provided at a pair of the supporting members 1 to prevent the removal preventing tool 11 for the plug P from being pivoted downward from the inlet portion Q of the plug P. The removal preventing tool 11 for the plug P is composed of a substantially reverse U-shaped holding frame 12 and arm portions 13 extending from both ends of the holding frame 12 and pivotably installed in holes 2 in a pair of the supporting members 1 arranged so as to face both ends of the inlet portion Q.