A connecting device for piping is disclosed. The connecting device for piping includes a connecting device body having therein ball insertion holes, balls inserted into the ball insertion holes so as to come into close contact with the outer surface of a pipe, a locking cap including a locking cap body movably coupled to the connecting device body and a pressing rim portion pressing the balls, a locking cap spring pressing the locking cap toward the position at which the locking cap contacts the balls, a stopper cap movably coupled to the connecting device body so as to limit movement of the locking cap, a plunger including a plunger body, a plunger tube inserted into the pipe, and a packing disposed on the periphery of the plunger tube so as to come into contact with the pipe, and a plunger spring pressing the plunger toward the pipe.