The invention provides a flash memory apparatus. In one embodiment, the flash memory apparatus comprises a flash memory and a flash memory controller. The flash memory comprises a write circuit and a memory cell array comprising a plurality of memory cells, wherein the write circuit is coupled to the memory cell array to write data in the memory cells. The flash memory controller is coupled to the write circuit, obtains a total capacity and a used data amount of the flash memory, and directs the write circuit to perform data writing in a one-bit mode when a ratio of the user data amount to the total capacity is less than a first predetermined value.