A golf club shaft (1) in which a difference between a maximum EI value and a maximum EI value in the range from a tip (1a) to a position spaced therefrom at a distance corresponding to not less than 40% nor more than 60% of the whole length of the shaft (1) is set to less than 10% of the average of the maximum EI value and the minimum EI value in the range. The diameter of the tip (1a) of the shaft (1) is set to not less than 9.0 mm nor more than 12.0 mm. The shaft (1) is applied to an iron club set consisting of a plurality of iron golf clubs having different numbers.