A grain boundary-insulated semiconductor ceramic contains a SrTiO3-based compound as a main component, and a diffusing agent containing a grain boundary insulating agent and a glass component. The grain boundary insulating agent is composed of a material free of lead, the glass component mainly contains a SiO2—X2O-MO—TiO2-based glass material that does not contain boron or lead and in which X represents an alkali metal, and M represents at least one of barium, strontium, and calcium, and the content of the glass component is 3 to 15 parts by weight relative to 100 parts by weight of the grain boundary insulating agent. A component base is composed of the grain boundary-insulated semiconductor ceramic.