An oxide superconductor in the Bi, Pb–Sr–Ca–Cu–O system has been prepared by the sol-gel method, and the effect of calcination temperature on the formation of the high-$T_{\text{c } }$ phase has been examined. Calcination at 830°C before the reheat treatment at 845°C is the most effective for the formation of the high-$T_{\text{c } }$ phase, as revealed by X-ray diffraction analysis. From this fact, we conclude that the nucleation of the high-$T_{\text{c } }$ phase is apt to take place at around 830°C. The $T_{\text{c } }$ value of the specimen calcined at 830°C and reheated at 845°C for 24 h is 90 K.