To obtain a pulse width modulation system that can enhance a transmission efficiency and a recording efficiency of data.

The pulse width modulation system is provided with a means that applies Fourier transform to a signal to be modulated to separate the signal into a plurality of different frequency components, a period detection means that measures a period of each of frequency components, a peak detection means that measures a maximum level of the signal to be modulated for the period of each frequency component, and a pulse generating means that generates a pulse with a width corresponding to either of the period and the maximum level, generates a pulse signal with a level corresponding to the period and the other maximum level on the basis of the pulse interval, composites the pulse signals of each frequency component and provides an output. Preferably, the period outputted to the pulse generating means is multiplied with n (n is a value different from each frequency component) and the maximum level is multiplied by m.