To easily connect a grounding line of indoor wiring which is led to an electrical distribution panel.

A grounding relay terminal 41 to which a ground line is connected is arranged in a case 1. The ground relay terminal 41 comprises an oblong insulating cover 42, which is formed on the front side so that a plurality of insert holes 43 and button holes 44 which open frontward, are arrayed in a single row, a locking connection terminal 50 that faces the insert hole 43, and a pair of screw connection terminals 55 provided at both ends of the array of the locking connection terminal 50. Operation of a release button 54 is easy, coping with both the connection methods, for the locking connection terminal 50 and the screw connection terminal 55. The locking connection terminal 50 facilitates connecting of the ground line; since the release button 54 of the locking connection terminal 50 is provided, biased to the outside of the case 1 relative to the insert hole 43, the grounding line connected to the locking connection terminal 50 will not interfere, when the release button 54 is operated.