To assure the loft angles capable of optimizing the differences in carries between the shaft numbers of respective clubs of a golf club set consisting of plural pieces of the clubs by setting the loft angles at the clubs of the respective shaft numbers by the differences in the carries between the adjacent shaft numbers.

The relations between the carries of hit balls and the loft angles are previously recognized with club lengths as parameters by experiment in the case of setting the loft angles. Namely, the clubs varying in the loft angles by each of the prescribed club lengths are manufactured and the balls are hit with these clubs by a robot machine. The carries are then measured and are graphed. For example, the number of pieces of the clubs are set at nine pieces (n=9) from #3 (No. 3 iron) to SW(sand wedge) and first, the differences in the carries between the adjacent shaft numbers are set at the desired values with the shaft numbers of the respective clubs. Next, the club lengths and the loft angles are properly set in the relation diagram of the carries and the loft angles with the club lengths as the parameters.