A vehicle air-conditioning system includes a solar radiation amount detection element configured to detect the amount of solar radiation incident on an instrument panel, a temperature correction element configured to correct a detection signal value output from the solar radiation amount detection element according to a temperature on the instrument panel, a solar radiation sensor configured to output a detection signal in which a temperature is corrected by the temperature correction element, and an air conditioner configured to control air conditioning inside a vehicle based on the detection signal from the solar radiation sensor.