In a memory device having a content addressable memory array and a random access memory array, the word coincidence lines and word selection lines of the content addressable memory array are connected to the word selection lines of the corresponding words of the random access memory array via a selection circuit, access is made to the random access memory array on the basis of the result of association of the content addressable memory array when the selection circuit selects the word coincidence lines, and access is made to the memory device as a whole as a random access memory array when the selection circuit selects the word selection lines.