PURPOSE: To fix completely a balance weight to a crank shaft by making the balance weight to touch the eccentric shaft portion of the crank shaft, and abutting an end of the eccentric shaft of the crank shaft to a receiving top to hold a caulking load of a punch by the top through an eccentric member.

CONSTITUTION: A balance weight 2 is plastically made of steel plate, and the whole circumferential edge of a fixing hole 2a on a face 2c on the counter-eccentric shaft side of the balance weight 2 is deformed by means of a punch 15 having a V-like section to caulk the balance weight 2 to a crank shaft 1. In this case, the balance weight 2 is made to touch an eccentric shaft portion 1b of the crank shaft 1 and also the end of the eccentric shaft portion 1b of the crank shaft 1 is made to abut on a receiving top 16. Consequently, due to holding effect of top 16 for caulking load of the punch 15 through the eccentric shaft portion 1b complete fixing, light weight and improved productivity can be obtained.