Abstract: A memory control method and a memory control device each suitable for information processing systems such as multiprocessing systems where plural data processing systems concurrently execute an operating process, and more particularly a memory control method and a memory control device each of which controls the data holding state of a buffer memory unit arranged in each of data processing units on a store-in basis to gain high speed access to the main storage unit. The memory control device issues a predetermined process command to be sent to the buffer memory unit in the data processing unit, and sets a flag showing a process under request, to a portion to be processed by the predetermined process command in a tag copying unit in the memory control device. Information regarding whether a block including a process request address exists in the buffer memory unit and whether the block is being processed currently are simultaneously obtained by retrieving only the tag copying unit.