Disclosed is a MOS transistor resistor that is equipped with a first MOS transistor (M1), which is used as a resistor, an input voltage source (1), which is connected, and applies an input voltage (Vin), to the source of the first MOS transistor, and a gate voltage source (6), which is connected, and applies a gate voltage (Vg), to the gate of the first MOS transistor. The gate voltage (Vg) and input voltage (Vin) are set in a range to cause the first MOS transistor to operate with the gate-source voltage and the source-drain voltage in the first MOS transistor in the unsaturated zone, and are set so that the temperature characteristics at the resistance value of the first MOS transistor become constant. Fluctuations in resistance value, which are caused by changes in leakage current due to manufacturing variances, are decreased and excellent temperature characteristics are obtained.