PURPOSE: To measure resistance value of a plurality of resistors with high accuracy continuously, by connecting a capacitor and an NOT circuit in series alternately and connecting a power supply to an input terminal of each NOT circuit via a measured resistance.

CONSTITUTION: When a microcomputer 16 outputs a rectangular wave, this rectangular wave is inverted at an NOT circuit 22 and inputted to a capacitor 10A, then the input terminal (c) of the NOT circuit 12A has a voltage drop once and the capacitor is being charged with charged supplies from a resistor 14A. Thus, a voltage which is at high level for a time of charging until the capacitor 10A is charged up to the threshold value, appears at an output terminal (d). This voltage change is inputted to the microcomputer 16 and a resistance value of the resistor 14A is calculated. On the other hand, the output of the output terminal (d) becomes a start signal of a next capacitor 10B, and resistance values for resistors 14b,... are obtained similarly, and the result of calculations is printed out on a printer 20 via an interface 18.