A liquid property sensor for detecting property of liquid includes a semiconductor board, a first electrode and a second electrode, and a protection film. The first and second electrodes are disposed on the semiconductor board to be spaced from each other at a predetermined distance. The protection film has resistance relative to the liquid, and is exposed to the liquid. The first and second electrodes detect a capacitance therebetween as the property of the liquid in accordance with a relative permittivity of the liquid. A capacitance-voltage conversion circuit of the semiconductor board converts the capacitance into a voltage value.