To provide a connecting device for a pipe joint with built-in heating wires allowing easy and exact piping.

This connecting device for the pipe joint with built-in heating wires is provided with a female screw 3a in the inner peripheral surface of a tip of a socket 11, in which heating wires 12 are not embedded, and a male screw 3b in the outer peripheral surface of a tip of a synthetic resin pipe 2. The female screw 3a of the union joint 1 and the male screw 3b of the synthetic resin pipe 2 are screwed to each other for fixation, and the heating wires 12 are heated to fuse the inner peripheral surface of the socket 11 and the outer peripheral surface of the end of the synthetic resin pipe 2 for connection.