A controller included in a flash memory system, which can be applied to a memory interface of a host computer is disclosed. A buffer is used for data exchange operation between the host computer and the controller, and data exchange operation between a flash memory and the controller. A host interface control block as a first control block controls data exchange operation between the buffer and the host computer. A flash sequencer block as a second control block controls data exchange operation between the buffer and the flash memory. The host interface control block controls input and output operation of the buffer, based on a memory control signal and a memory address signal supplied from the host computer. The flash sequencer block controls input and output operation of the buffer at a one-page size of the flash memory.