PURPOSE: To decrease a reading access time by arranging memory cells including sequential memory arrays in the plural odd numbered columns and the plural even numbered columns and connecting an output buffer with a detection means for generating data during an alternate reading cycle.

CONSTITUTION: A sequential memory array 12 is comprised of plural memory cells, which are arranged in the plural odd numbered columns COL 1, COL 3 and the plural even numbered columns COL 2, COL 4. A detection means 10 is provided in order to interleave data stored in the memory cells in the odd numbered columns with those stored in the memory cells in the even numbered columns. An output buffer 16 is connected with the detection means 10 in order to generate output data which alternately represent the data stored in the odd and even numbered columns during the alternate reading cycle. Thus, since a reading mode is used on alternate cycles so as to be generated over a span of two cycles, the reading access time can be shorten.