Weighted inequality on the Hardy-Littlewood maximal function is completely understood while it is not well understood for the spherical maximal function. For the power weight $|x|^{alpha}$, it is known that the spherical maximal operator on $R^d$ is bounded on $L^p(|x|^{alpha})$ only if $1-dleq alpha<(d-1)(p-1)-1$ and under this condition, it is known to be bounded except $alpha=1-d$. In this paper, we prove the case of the critical order, $alpha=1-d$.