To restrain failure in forming a screw when a main body fitting for a spark plug is manufactured.

A method for manufacturing a main body fitting for a spark plug includes a step for preparing a die having an inner hole communicated by a large diameter hole and a small diameter hole, a shearing step for obtaining a metallic start material by shearing a wire material into a predetermined length, a step for forming a raw material diameter part on the starting material by inserting the starting material in the inner hole from the large diameter hole side of the die and extruding it to the small diameter hole side for performing forging, a step for cutting an outer periphery in a predetermined cutting range from a tip of the raw material diameter part, and a step for forming a screw on the outer periphery out of the cutting range of the raw material diameter part. In this method, an edge of a tip surface of the starting material generated in the shearing step is within the cutting range after forging.