To provide a resin pipe welding apparatus for welding the same resin as the material of a resin pipe to the whole inner peripheral surface of the joined part of the resin pipes so as not to more rapidly deteriorate a seal than the material of the resin pipe, a resin pipe welding method and the joint structure of the resin pipe.

In the welding of two resin pipes K and K, both inner side edges of the opposed end surfaces of two resin pipes K and K are chamfered and the chamfered space, the space between the opposed end surfaces and the space between the outside required regions of the resin pipes K including both outside edges of the opposed end surfaces are filled with a welding resin J not only to weld and join the resin pipes but also to bridge them.