PURPOSE: To reduce the circuit scale by providing the plural number of current control circuits for a current integration type delta demodulator, synthesizing currents converted by the plural number of current control circuits, and integrating the result by one integration circuit.

CONSTITUTION: First and 2nd digital signals D1, D2 coded by delta modulation are inputted to a current integration delta demodulator Z comprising 1st, 2nd current control circuits 1, 2 and an integration device 3 via input terminals 8, 9. The digital signals D1, D2 are converted into currents having the level and the direction in response to the content of codes of the signal by the 1st, 2nd current control circuits 1, 2. The converted currents are synthesized and the resulting current is supplied to the integration device 3. An analog signal A3 corresponding to the sum of the digital signals D1, D2 is outputted from the integration device 3. Since the output currents of the 1st, 2nd current control circuits 1, 2 are summed and the resulting current is supplied to the one integration device 3 in such a way, the interference between outputs of integration devices is evaded and the same number of integration devices and buffer amplifiers as the number of digital signals is not required. Thus, the mixing circuit with a small circuit scale is realized.