Provided is an apparatus for calculating an absolute difference capable of efficiently performing an absolute difference using an adder. The apparatus for calculating an absolute difference includes a comparator comparing values of two integers, first and second selectors each selecting and outputting one of the two integers according to the comparison results of the comparator, an inverter complementing the result value selected by the second selector; and an adder adding up the result value selected by the first selector, the value complemented by the inverter, and 1.