A memory test device, including a universal register to conduct an operation by a predetermined universal command language; an extension register having a larger capacity than the universal register and to conduct an operation by a predetermined extension command language; and a controller to write a predetermined test pattern in an external memory using the extension command language, to read the test pattern written in the memory, to determine the identity of the written test pattern and the read test pattern, and to determine a presence of an error in the memory using the universal command language.