PURPOSE: To obtain a highly accurate operating device, by providing a function selecting a register inputted with the number of times of sampling for a circuit which A/D-converts an instantaneous value of an analog quantity, D/A-converts data of the register and obtains an average value.

CONSTITUTION: A value x1 converted from an input analog quantity into a digital quantity at an A/D converter 1, passes through a switch 81 controlled at a control section 7, and is inputted to a register R1. A nect data x2 passes through 81', is inputted to R1' and the operation of 1/2(x1+x2) is made at an operation device 91, the result is inputted to a register R2 and the switch 81 resets the R1. The next input data passes through the switch 81 and is inputted to the R1. Similarly, the operation is made up to a register Rk. The output of the R1WRk is D/A-converted 51W5k into analog quantity. The number of times of sampling is inputted to a counter 10 with the control section 7, converted into the analog quantity at a D/A converter 5k+1 and inputted as a denominator of dividers 111W11k. The output of the dividers is inputted to an adder 12 and the output is an average value.