To manufacture a golf club which has a proper frequency and a proper flexibility matching the head speed by a player even though the lengths of the golf clubs are different.

When the head speed of a driver shot by a player is set to (v) (m/sec); the proper frequency of a club, F (freq./sec); the length in measurement of frequency, L (m); and the proportion coefficient, (b); the rigidity of a golf club shaft is adjusted so that the proper frequency of the shaft satisfies a relation F=3√ (b.v)/L. The length L in measurement of frequency is calculated by contracting 0.178 m (7 inches) from the club length. The standard value of the proportion coefficient (b) is 1.5. When measurement units are set to custom of the golf world, length in inch and frequency in freq./min, the standard value of (b) becomes 1.98×1010.