In the present invention, focusing on the point that the number of transistors can be reduced to about 2/5 of that in a prior art due to an absolute-value-of-difference calculating circuit for an associative memory being configured of two of an addition circuit and a bit inversion circuit. The absolute-value-of-difference calculating circuit is built in a fully-parallel type associative memory as a unit comparison circuit (UC), and all of the outputs of the absolute-value-of-difference calculating circuits (UC ij ) for which the number of comparisons thereof are prepared are input to weight comparison circuits (WC ij ), whereby the calculation of the Manhattan distance between the search data (SW) and the reference data (REF) is carried out. In accordance with the configuration, because a Manhattan distance calculating circuit can be realized by a fewer number of transistors and with a small area, an associative memory apparatus as well can be realized at a low power consumption and with a small area.