PURPOSE: To attain the adjustment with one operation when two D/A converters are used for one adjustment item.

CONSTITUTION: An LSB of a 2nd D/A converter 3 is added to an LSB of a 1st D/A converter 2 at a weighting adder circuit 4 so that the LSB of the 2nd D/A converter 3 corresponds to the 1/4 LSB of the 1st D/A converter 2. A D/A converter control means 5 increases the conversion rate of the 2nd D/A converter 3 step by step each by the operation of a switch 6, decreases the conversion rate of the 2nd D/A converter 3 by 8 steps when the rate is increased by 8 steps, and increases the conversion rate of the 1st D/A converter 2 by one step simultaneously. The conversion rate is decreased similarly by the operation of a switch 7. A step difference takes place in a data change, both D/A converters 2, 3 are interlocked by one operation and the step difference is adjusted by the accuracy of the 2nd D/A converter 3.