A digital control device for tracking a sine wave according to the present invention has a compensator, a control object and a feedback gain. An input into the compensator is a signal obtained by subtracting a control quantity from a reference value. An input into the control object is a signal obtained by subtracting an output of the feedback gain from an output of the compensator. A transfer function of the compensator is (k.sub.2z+k.sub.1)/(z.sup.2-2z cos .omega.T+1), where .omega. is an angular frequency, T is a sampling period, z is a z operator, and k.sub.1 and k.sub.2 are constants. Thus, a second-order compensator can be configured, with which a sinusoidal reference waveform can be tracked simply and with high accuracy.