A memory device system of the present invention is equipped with a memory device comprising a first memory unit for storing data, and a second memory unit for storing an access log regarding an access to the first memory unit; a port for inputting and outputting data; a control device for writing the access log in a memory area other than the area, where the access log is already written in the second memory unit, if an access request to the first memory unit is input through the port and the access log is written in the second memory unit according to the access request, and for prohibiting a write in the second memory unit if an information write request in the second memory unit is input through the port.