To provide a motor starting circuit capable of operating normally even if an inexpensive triac is used.

A motor starting circuit 1 starts a motor 12 that includes an auxiliary coil 12b operating at the time of starting and a main coil 12a operating during the normal operating state, by receiving the supply of an AC voltage of 200 V or more to 220 V or less. A thermistor 20 is connected in series to the auxiliary coil 12b. A triac 24 is connected in series to the auxiliary coil 12b and the thermistor 20. A thermistor 22 is connected to a gate of the triac 24 and is connected in parallel to the thermistor 20, includes a thermistor element assembly forming a rectangular parallelepiped having a volume of 1.5 mm³ or more to 10 mm³ or less, and has a resistance value of 800 Ω or more to 3000 Ω or less at 25°C.