A method and apparatus for detecting a free page of a memory device, and a method and apparatus for decoding an error correction code by using the method and apparatus for detecting a free page are provided. Free page data read from the memory is converted into a converted codeword for inclusion as an element of an error correction code field. The converted codeword is compared to an initially set target codeword to detect an amount of non-identical bits. A page read from the memory is determined to be a free page when the amount of non-identical bits is equal to or less than an initially set threshold value.