A thermistor sintered body comprising a sintered body that comprises: more than 50% by volume to 90% by volume of a Y 2 O 3 phase as a main phase; 10% by volume to less than 50% by volume of a Y(Cr, Mn)O 3 phase as a sub-phase dispersed in the main phase; and Ca dissolved in the Y(Cr, Mn)O 3 phase, characterized in that the sintered body has a composition in which 0 ≤ Cr/Mn < 1.0 so that the sintered body is rich in Mn relative to Cr, the sintered body has a crystal structure of an orthorhombic crystal system, and the sintered body satisfies one of the following conditions (a) to (b): (a) the sintered body comprises a Y(Cr, Mn)O 3 phase as the sub-phase, and comprises 3 to 9 mol% of Cr, 5 to 15 mol% of Mn, 1 to 8 mol% of Ca, and a balance of Y, wherein Cr/Mn is 0.4 to 0.9 and calculation of the molar percentages of Cr, Mn, Ca and Y does not take into account the amount of oxygen comprised by the sintered body; or (b) the sintered body comprises a Y(Cr, Mn)O 3 phase as the sub-phase, and comprises ≤5 mol% (excluding 0) of Cr, 12 to 23 mol% of Mn, 6 to 18 mol% of Ca, and a balance of Y, wherein Cr/Mn is 0.5 or smaller (excluding 0) and calculation of the molar percentages of Cr, Mn, Ca and Y does not take into account the amount of oxygen comprised by the sintered body; such that a B constant (B(0/1000)) of the sintered body determined by the following expression is 2400 K or lower and 2185 K or more: B = lnRm − lnRn / 1 / Tm − 1 / Tn, wherein ln: natural logarithm, Rm: resistance value at 273 K, Rn: resistance value at 1273 K, Tm: 273 K, and Tn: 1273 K. more than 50% by volume to 90% by volume of a Y 2 O 3 phase as a main phase; 10% by volume to less than 50% by volume of a Y(Cr, Mn)O 3 phase as a sub-phase dispersed in the main phase; and Ca dissolved in the Y(Cr, Mn)O 3 phase, characterized in that the sintered body has a composition in which 0 ≤ Cr/Mn < 1.0 so that the sintered body is rich in Mn relative to Cr, the sintered body has a crystal structure of an orthorhombic crystal system, and the sintered body satisfies one of the following conditions (a) to (b): (a) the sintered body comprises a Y(Cr, Mn)O 3 phase as the sub-phase, and comprises 3 to 9 mol% of Cr, 5 to 15 mol% of Mn, 1 to 8 mol% of Ca, and a balance of Y, wherein Cr/Mn is 0.4 to 0.9 and calculation of the molar percentages of Cr, Mn, Ca and Y does not take into account the amount of oxygen comprised by the sintered body; or (b) the sintered body comprises a Y(Cr, Mn)O 3 phase as the sub-phase, and comprises ≤5 mol% (excluding 0) of Cr, 12 to 23 mol% of Mn, 6 to 18 mol% of Ca, and a balance of Y, wherein Cr/Mn is 0.5 or smaller (excluding 0) and calculation of the molar percentages of Cr, Mn, Ca and Y does not take into account the amount of oxygen comprised by the sintered body; (a) the sintered body comprises a Y(Cr, Mn)O 3 phase as the sub-phase, and comprises 3 to 9 mol% of Cr, 5 to 15 mol% of Mn, 1 to 8 mol% of Ca, and a balance of Y, wherein Cr/Mn is 0.4 to 0.9 and calculation of the molar percentages of Cr, Mn, Ca and Y does not take into account the amount of oxygen comprised by the sintered body; or (b) the sintered body comprises a Y(Cr, Mn)O 3 phase as the sub-phase, and comprises ≤5 mol% (excluding 0) of Cr, 12 to 23 mol% of Mn, 6 to 18 mol% of Ca, and a balance of Y, wherein Cr/Mn is 0.5 or smaller (excluding 0) and calculation of the molar percentages of Cr, Mn, Ca and Y does not take into account the amount of oxygen comprised by the sintered body; such that a B constant (B(0/1000)) of the sintered body determined by the following expression is 2400 K or lower and 2185 K or more: B = lnRm − lnRn / 1 / Tm − 1 / Tn, wherein ln: natural logarithm, Rm: resistance value at 273 K, Rn: resistance value at 1273 K, Tm: 273 K, and Tn: 1273 K. ln: natural logarithm, Rm: resistance value at 273 K, Rn: resistance value at 1273 K, Tm: 273 K, and Tn: 1273 K.