PURPOSE: To facilitate the assembling work and at the same time improve the productivity by a method wherein a hot welder is rendered to be pivotable at arbitrary angle.

CONSTITUTION: A rotating table 5, on which a high frequency heater 2 is fixed, is made pivotable about a hinge 6 from 0W90°. The high frequency heaters 2 are brought into positions standing in front of workers by properly changing the angles of the rotary tables 5 so as to be within their reach, resulting in enabling to easily arrange materials to be welded on the high frequency heaters 2 by a fewer workers than ever. The provision of a hydraulic cylinder between the rotating table 5 and a table 1 or the rotation of the center shaft of the hinge 6 is also acceptable. It is acceptable to design the whole high frequency welder as a type inclined at a required angle or to make the inclination of the hot welder changeable to a required angle.