Abstract: A content addressable memory (CAM) comprises a plurality of CAM cells, a CAM cell block comprising the CAM cells, a CAM array arranging a plurality of the CAM cell blocks to the row direction, a work line arranging a predetermined direction in each of the CAM cell blocks, a block matching line for outputting a result of a retrieval operation in the CAM cells connected to the same word line in the same CAM block and installed corresponding to the same word line, an array matching line for outputting the result of the retrieval operation output to the block matching line, and transfer circuits for transferring the result of the retrieval operation to the array matching line. Another CAM further comprises masking circuits for masking retrieval data at a predetermined CAM block.