Superconducting Ba1.8R0.2*RCu3Oz (R*, R=La, Nd, Sm, Gd, Dy, Y) cuprates are prepared at 0.1 MPa and 2 GPa to study the relationships between composition, structure and superconducting critical temperature (Tc). The oxygen contents (z) of the cuprates annealed in oxygen range from 7.00 to 7.07 per formula unit. Tc varies depending on the oxygen content and the kind of rare-earth elements on the Ba site. High La contents on the Ba site are favorable for high Tc values, whereas Y, Dy and Gd on the Ba site suppress Tc. Tc tends to increase with increasing ionic radii of rare-earth elements. A similar result is obtained for cuprates with z≈7.10 annealed at 1.5 GPa. The results are explained in terms of the hole distribution between CuO2 sheets and BaO–CuOx layers. The large number of hole carriers in the CuO2 sheets is reduced by the partial replacement of Ba with rare-earth elements that have smaller ionic radii.