A temperature sensor that includes an organic-inorganic composite negative temperature coefficient thermistor and a transistor. The organic-inorganic composite negative temperature coefficient thermistor includes a thermistor layer which includes spinel-type semiconductor ceramic composition powder containing Mn, Ni and Fe and an organic polymer component, and a pair of electrode layers. The semiconductor ceramic composition powder has a molar ratio of Mn to Ni of 85/15≥Mn/Ni≥65/35 and a Fe content of 30 parts by mole or less when a total molar amount of Mn and Ni is regarded as 100 parts by mole, and has a peak with a local maximum value of around 29° to 31° in its X-ray diffraction pattern, a half width of which peak is 0.15 or more. The transistor is electrically connected with either one of the pair of electrode layers.