To provide a wheel speed detecting device capable of precisely monitoring wheel speed information.

The wheel speed detecting device outputs wheel speed information (first wheel speed) based on information on the angular frequency of an AC signal outputted from a wheel speed sensor 10. The AC signal is converted into a square wave signal and the wheel speed information is monitored based on the period (second wheel speed) of the square wave signal. Since square waves have high noise resistance, precise monitoring of wheel speed information can be effected.