A semiconductor ceramic contains erbium as a semiconducting agent in primary components of barium titanate, strontium titanate, lead titanate and calcium titanate, with the average grain diameter of the semiconductor ceramic exceeding about 5 &mgr;m but not exceeding about 14 &mgr;m. Further, the semiconductor ceramic contains as additives a compound containing Er with the Er being more than about 0.10 mol but no more than about 0.33 mol, a compound containing Mn with the Mn being about 0.01 mol or more but no more than about 0.03 mol, and a compound containing Si with the Si being about 1.0 mol or more but no more than about 5.0 mol, per 100 mol of the primary component. Thus, a semiconductor ceramic and positive-temperature-coefficient thermistor can be provided with high-flash-breakdown capability, excellent results in ON-OFF application tests and few irregularities in resistance values.