A semiconductor ceramic includes a BaTiO3-based composition, as a main component, having a perovskite structure represented by general formula AmBO3. Part of the A site Ba is replaced with an alkali metal element, Bi, Ca, Sr, and a rare-earth element. When the molar amounts of Ca and Sr are x and y, respectively, and the total number of moles of the elements constituting the A site is 1 mole, 0.05≦x≦0.20, 0.02≦y≦0.12, and 2x+5y≦0.7. A PTC thermistor includes a component body formed of the semiconductor ceramic. Even when an alkali metal element and Bi are present, there is provided a lead-free semiconductor ceramic with high reliability in which the surface discoloration is not caused and the degradation of resistance over time can be suppressed even after the application of an electric current for a long time.