Each point obtained by plotting flexural rigidity EI measured at ten sites on a shaft is defined as from T(1) to T(10) in this order from the head side, and the formula representing a line K that passes the T(1) and the T(10) is [Y=aX+b1]. The values at the Y-intercepts on the lines that are parallel to the line K and that pass the points of from T(2) to T(9), respectively, are defined as from b2 to b9, respectively, and the minimum value among the values at the Y-intercept b2 to b9 is defined as bmin. In this shaft, slope "a" of the line K is 0.04 or greater and 0.06 or less; any one of the b3, b4, b5, b6, b7 and b8 is smaller than b1; and the bmin is any one of b4 to b7. The value (b1-bmin) is 24 (Nm.sup.2) or greater and 35 (Nm.sup.2) or less, and the value (b9-b1) is 0 or greater and 10 (Nm.sup.2) or less. This shaft achieves excellent flight distance performance and directionality of the hit ball.