PURPOSE: To ensure an extremely easy balancing process for a crankshaft and the like by punching preliminarily small bores on the balancing processing part thereof before the application of austempering treatment and drilling the small bores after the austempering treatment.

CONSTITUTION: Before austempering, small bores 4, 4 and so forth are punched on each balance weight part 3. Thereafter, austempering applies and a crankshaft A is heated and retained at a temperature of approximately 900°C for one hour or so, then quenched to approximately 300°C to 400°C in a salt bath and retained for approximately one to two hours. After the austempering treatment applies, the balancing process of the cooled crankshaft A is carried out with the small bores 4, 4 and so forth punched on the balance weight 3, using a drill 5 of diameter larger than the bore 4. As a result, the chisel part 5a of the drill 5 is almost free from cutting resistance, thereby making a drill wear small and ensuring an extremely easy balancing process.