PURPOSE: To improve the conversion accuracy by converting once a binary signal inputted to a bit input terminal group into a pulse width modulation wave and then converting it into an analog signal.

CONSTITUTION: The 1st bit of a binary signal being binary-conversion of a sampling value at each period T of an analog signal is inputted to the 1st bit input terminal I1 and the N-th bit is inputted to the N-th bit input terminal In in a bit input terminal group I. A pulse signal generator P generates a pulse signal having a constant pulse width T2N and a period TK=T/2K-1. The gate circuit group G is provided with the K-th gate circuit GK where the K-th pulse of the generator P is switched by a signal of the K-th bit input terminal IK of the terminal group I. An OR circuit S sums only 1 digits of each output of each gate circuit and the output is a pulse width modulation of the input signal of the terminal group I. An LPF circuit F integrates the output of the circuit S to obtain an analog signal before conversion.