There are provided a signal duty detecting apparatus detecting a duty of a pulse width modulation (PWM) signal by counting a signal, among signals present in a preset period of the PWM signal, having a predetermined level or higher and a motor driving apparatus having the same. The signal duty detecting apparatus includes: a level detector detecting levels of an input signal; a counter counting the levels detected by the level detector; and a duty calculator calculating a duty of the input signal based on the levels counted by the counter.