PURPOSE: To improve the balance of the respective electric characteristics of a capacitor by forming the insulated layer of oxide contg. Bi, Cu and Cs to the grain boundary of a porcelain sintered body consisting of SrTiO3, BaTiO3, a valency controlling agent and a sintering adjuvant.

CONSTITUTION: 005-0.40 mol Nb2O5 and/or Y2O3 as a valency controlling agent and 0.10-0.40mol CuO and/or MnO2 as a sintering adjuvant are mixed with 100mol main component consisting of 97-80mol SrTiO3 and 3-20mol BaTiO3 and this mixture is sintered. In order to insulate the grain boundary layer of the obtained porcelain sintered body, the sintered body is coated with composition which incorporates a mixture obtained by mixing 20-98mol% Bi2O3, 1-30mol% CuO and 1-70mol% carbonate or oxide of Cs as a main raw material and thereafter roasted. Thereby the respective electric characteristics of a capacitor are improved with good balance. Grain boundary insulation type semiconductor porcelain is obtained which is especially good in both dielectric constant and degree of temp. change in electrostatic capacity.