An analog/digital converter which has two comparators and, when the first comparator is successively given an analog voltage and a reference voltage and is comparing the two values, the second comparator is given the analog voltage or the reference voltage and is put in setup state, while when the second comparator is comparing the voltages, the first comparator is put in setup state, so that the comparison operation and the setup operation of the comparators are carried out in parallel, thereby increasing the rate of supplying the results of comparison.