An object is to provide a thermoplastic tube bending method that suppresses springback after the processing by a highly safe and short bending step. The thermoplastic tube bending method includes a step S1 of preheating the thermoplastic tube, a step S2 of bending the preheated thermoplastic tube by using a forming mold, and a step S3 of forming the bent thermoplastic tube by temperature control of an electric heater provided to the forming mold.