A fluid property detecting device includes a detection portion configured to detect electric characteristics of a detection target fluid, a calculation portion configured to calculate a property value of the detection target fluid, and a storage portion configured to store the property value calculated by the calculation portion. The storage portion stores, in advance, as the reference detection value, the detection value of the electric characteristic of a reference fluid detected by the detection portion, and the calculation portion calculates the property value of the detection target fluid on the basis of a value obtained by subtracting the reference detection value from a detection value of the detection target fluid.