PURPOSE: To use only one digital comparator irrespective of the number of digits of a BCD signal, and to decide in a short time whether said signal is large or small, by comparing two multi-digit binary-coded-decimal code signals BCD in order from the upper digit.

CONSTITUTION: In case a BCD signal A is 0424, and B is 0415, they are compared successively from the upper digit by a digital comparator 4, and if numerical values of each digit are equal, a dissidence signal is "O", and is they are not equal, a dissidence signal 1 is generated to an A>B output or an A<B output by A>G or A<B. Therefore, as a result of comparison of the BCD signals A, B, 0010, and a dissidence signal of a binary number of 0001 are obtained in the A>B output and the A<B output, respectively. Each dissidence signal is read in shift registers 6, 7, respectively, and sizes of both of them are compared by a 4-bit comparator 8, and in this case, it is decided to be A>B. This result is latched by an RS latch 9, and also a signal is outputted to a clock generator 10, and the comparing operation is ended.