The invention relates to a manufacturing method of a toilet seat. Scratches caused by vibration welding or ultrasonic welding difficultly occur on a seat surface or a bottom surface. According to themanufacturing method of the toilet seat (1) with a seat (2) and a bottom (3), a seat surface (21) is formed on the upper surface of the seat, a seat inner circumferential welding position (221) is located on the lower end surface of an inner circumferential end (22), a seat outer circumferential welding position (231) is located on the lower end surface of an outer circumferential end (23), and aseat inward protrusion part (251) and a seat outward protrusion part (252) are formed. A bottom inner circumferential welding position (311) is located on the upper surface of an inner circumferentialend (31) of the bottom, and a bottom outer circumferential welding position (321) is located on the upper surface of an outer circumferential end (32). The seat is installed on a seat push fixture (5) and is pushed to the bottom side during welding. The seat push fixture is used for pushing so as to form a clearance (7) between the seat surface and a noncontact part. The seat inward protrusion part and the seat outward protrusion part are removed after welding.