To reduce design time and design cost for a golf club shaft.

The method for designing the golf club shaft comprising fiber-reinforced resin includes a step of obtaining a shaft model which is numerically computable by computer by modelling a golf club shaft using a finite number of elements with which a plurality of design variables are defined, a step of computing a plurality of mutually different target functions representing performance of the shaft model set in the above step by computer, a step of generating an approximate relevant answer function to set relations between the design variables and the target functions by computing a number of combinations of the design variables and the target functions, a step of obtaining a plurality of solutions for optimizing the target functions based on the approximate relevant answer function, a step of obtaining Pareto solutions using a data comprehension analysis method out of the plurality of solutions obtained in the above step, and a step of setting the respective variables for the golf club shaft based on the Pareto solution.