A data writing method for writing data to a flash memory includes writing an initial value to the data storage area, determining whether or not the writing of the initial value is performed normally based on a write flag, writing data to the data storage area when the writing is performed normally, and erasing a block including the data storage area when the writing is not performed normally. An initial value is written to the data storage area before writing data, so that whether or not an error correction code storage area contains the initial value may be confirmed. An erase operation of the block is performed only when the error correction code storage area does not contain the initial value, so that the number of times of erasure of the block may be reduced and the life of the product may be increased.