Pulse-width modulation signal generating device and method for the same that can generate multiple pulse-width modulation signals with different overall lengths wherein only a small amount of data is stored in storage means and duty cycles are varied between individual unit pulse signals. Multiple settings are stored in storing means for three types of variables: initial duty cycle; duty change range; and number of unit pulse signals that form a single phase. Out of these, a selected initial duty cycle, a selected duty change range, and a selected number of unit pulse signals that form a single phase are retrieved. These selected values are used to represent the duty cycles for all unit pulse signals forming one phase. The unit pulse signals for which duty cycles have been determined are output to generate a pulse-width modulation signal.