A pulse modulation method divides code comprising 4N-bit data into 2-bit units of data. For each pulse signal having a fixed pulse width tw, a code modulated signal is generated by pausing between pulse pause intervals Tr. An adjusted time width of between ½ and 1 times the fixed pulse width tw is taken to be Δt. One of time widths 0, Δt, 2Δt, and 3Δt is added to a fixed pause period tm of time intervals according to a corresponding value of the 2-bit data. If the sum total time TD of the code modulated signal is an interval of at least [(2tw+2tm+3Δt)N+Δt], each pulse pause interval Tr is substituted by a pulse pause interval Tr corresponding to the inverted 2-bit data. An inversion flag signal expresses that inversion information is added to the code modulated signal.