It is intended to provide a method of producing thermally fused synthetic resin members for medical use which makes it possible that, in the case of thermally fusing synthetic resin members for medical use, for example, a relatively soft thermoplastic tube constituting an AVF needle with another part being harder than the tube such as a needle base (hub) of a wing needle, or a part provided with a fitting connector being harder than the tube (for example, a blood circuit, an extension tube, an infusion set or the like), the connecting parts of the thermoplastic tube member and the other member harder than the thermoplastic tube member can be quickly and uniformly thermal-fused and the production process can be automatically and continuously performed while keeping a high productivity and a production apparatus therefor.