PURPOSE: To efficiently and rapidly heat by a heater and to suppress a bead at the connecting part of thermoplastic resin tubes by mainly heating to melt the centers of the thick ends of the tubes, butting the ends, pressurizing the ends, and connecting them by fusion bonding.

CONSTITUTION: A spot heater 2 is provided at a predetermined interval substantially in parallel with the end face 11 of a straight-chain polyphenylene sulfide resin(PPS) tube 1. A reflecting plate 21 of a parabolic section is opposed to the end face 11 in a circular state along the end face 11 at the end face 11 side of the PDS tube 1 of the heater 2. A plurality of halogen lamps 22 are arranged at the center of the plate 21. The tube 1 is mainly heated to be melted at the center of the thick end 11 of the tube by the heater 2. Thus, a molten part is radially formed at the center of the end 11 as a starting point, and the center is slightly swelled toward the outside. Then the ends are butted, pressurized and connected by fusion bonding.