Abstract: A fitting device for selecting a golf club suitable for a golfer comprises: an acquisition part that acquires measurement values obtained by measuring a golfer's swing motion of a first golf club with a measuring device; and a calculation part that calculates a swing index related to the swing motion based on the measurement values; a determination part that determines, based on the swing index, a second optimum characteristic index indicating characteristics of a shaft for a second golf club different from the first golf club; and a selection part that selects at least a shaft for the second golf club that matches the second optimum characteristic index.