Cleavage plane surfaces of oxide superconductors, Bi₂Sr₂CuO_ν (2201 phase, T_c=20 K) and Bi₂Sr₂-Ca₂Cu₃O_ν (2223 phase, T_c= 110 K), are examined by the high-resolution electron microscope profile imaging method. It is confirmed that the surfaces consist of single Bi0 plane indicating that the crystal is cleaved in the middle of two (BiO) ₂ layers. It is also confirmed that incommensurate modulation in the bulk structure is preserved even at the cleavage plane to form wavy surface structure. The results are almost consistent with those previously reported for Bi₂Sr₂CaCu₂O_ν (2212 phase, T_c = 80 K).