A signal generating apparatus includes: a data generator which generates a data series in which first, second, third and fourth data are arranged at a sampling period; a first signal generator which generates a first pulse-width modulation signal in which a pulse is arranged in a pulse period longer than the sampling period, time points of front and rear edges of the pulse being set in response to the first and second data; and a second signal generator which generates a second pulse-width modulation signal in which a pulse is arranged between the adjacent pulses of the first pulse-width modulation signal, time points of front and rear edges of the pulse of the second pulse-width modulation signal been set in response to the third and fourth data, respectively.