The invention provides a data transfer method useful for data transfer with PC cards or other external equipment connected to a personal computer. First in a memory-to-memory data transfer mode, a part of data to be transferred is used as address data and the rest of the data to be transferred is stored at memory addresses specified by the address data. Next, in a block transfer mode, the data is transferred to a PC card or other external equipment. In this process, because transfer-source address data, i.e. part of the data to be transferred, is put on the address bus in the block transfer mode, the data is transferred with both address bus and data bus.