Many‐body effects in Cu 2px‐ray photoemission of Bi2Sr2CaxCu1+xO6+2x(x=0,1,2), La2−xSrxCuO4(x=0,0.13), and ErBa2Cu3O7−x,y(x<y) were observed and correlations between the many‐body effects and high‐Tcsuperconductivity of cuprate superconductors were reviewed. For the Bi2Sr2CaxCu1+xO6+2x(x=0,1,2) and La2−xSrxCuO4(x=0,0.13) systems, proper high‐Tcsuperconductivity was realized by increasing the transfer integral and the interaction strength of the Cu‐O bond of the crystal determined the superconducting properties. However, for the ErBa2Cu3O7−xand YBa2Cu3O7−xsystems, 90 K superconductivity was realized by increasing the charge transfer energy. The extended valence state including the Cu, Ba, and O valence states in the crystal determined the superconducting properties of the ErBa2Cu3O7−xand YBa2Cu3O7−xsystems.