PURPOSE: To improve reliability by providing another one data output buffer which outputs a logical level of a predetermined bit of stored data of a plurality of bits to be simultaneously read through other predetermined external terminal.

CONSTITUTION: A data output buffer DOB which outputs a logical level of a predetermined bit of stored data of a plurality of bits to be simultaneously read at the time of testing multiple bits through other predetermined external terminal is provided in a dynamic RAM, etc., having a multi-bit testing function of a binary output test mode. With such a configuration, the level is decided to match the compared collated result of the stored data of the plurality of bits to be simultaneously read at the time of testing multiple bits. Even if the level of the stored data is simultaneously inverted, it is detected to identify a malfunction of the RAM, etc.