To detect a horizontal or vertical load exceeding an allowance value acting on a gripping device.

This detector 40 has a supporting device 50 for gripping an electric wire D, a moving device 41 fixed to the device 50, and an alarm 60 for sounding an alarm buzzer 63 when horizontal force F applied from the wire D exceeds the allowance value. The moving device 41 has a pair of parallel shafts 43 juxtaposed inside a frame body 42, and moving members 44 movable along their axial center directions. The supporting device 50 is fixed onto the paired moving members 44, an intermediate shaft 71 is provided between tire parallel shafts 43, the first compression spring 73 and the second compression spring 75 are provided in the intermediate shaft 71, and a pressing member 46 is sandwiched to connect adjacently the paired moving members 44 each other between the springs. The springs are energized to a direction to prevent the moving of the moving members 43. When the load exceeding the allowance value is applied onto the supporting device 50, protruded pieces 47, 48 are brought into contact with limit switches 62, 69 provided in the alarm 60 to sound the buzzer 63.