A laminated PTC thermistor element includes: a ceramic substrate including a plurality of ceramic layers; a plurality of internal electrodes formed within the ceramic substrate; and external electrodes formed on the surface of the ceramic substrate, for providing electrical conduction to the internal electrodes. The ceramic substrate is 0.3 [µm] or more and 1.2 [µm] or less in average porcelain grain size. Furthermore, the relative density of the ceramic substrate has a lower limit of 70 [%], and an upper limit of -6.43d + 97.83 [%] when the average porcelain grain size is denoted by d.