A size comparing circuit adopts a configuration wherein bits of two binary numbers to be compared corresponding to each other are compared sequentially from the most significant bit (MSB) side by one-bit judging device, and when one bit is judged to be larger as a result of this comparison, the binary number containing that bit is judged to be larger, so that, in the case where each pair of bits are compared from the MSB side and the values of both bits corresponding to each other differ, the result thereof is found immediately.