We present our study of the dependence of the heavy-to-light semileptonic B decay form factors on the heavy-light meson mass M-PS. Simulations are made over a range of the heavy quark mass covering both the charm and bottom quarks using the O(a)-improved clover action at beta = 5.9 on a 16(3) x 40 and 24(3) x 64 lattice. We find that a weak dependence of form factors on M-PS observed in previous studies in the region of charm quark persists up to the region of b quark. The soft pion relation f(0)(q(max)(2)) = f(B)/f(pi) is examined and found to be largely violated.