Abstract: A method of bonding plastic pipes, which comprises heat-melting the outer circumferential surface of an end portion of a plastic pipe and the inner circumferential surface of a sockt portion of a plastic joint, and inserting the end portion of the plastic pipe into the socket portion of the plastic joint to thereby bond the two; wherein the inner circumferential surface of the socket portion of the plastic joint is tapered so that the socket portion becomes progressively smaller in diameter in a direction away from its end portion, or the outer circumferential surface of the end portion of the plastic pipe is tapered so that the end portion becomes progressively smaller in diameter toward its insertion end, and wherein when the end portion of the plastic pipe is to be heated, the length from its insertion end of a part to be heated is made nearly equal to the final insertion length of the pipe and when the socket portion of the plastic joint is to be heated, the length from the socket end of a part to be heat