An operating method of a memory is provided. The memory includes a memory cell array composed of a plurality of memory cells, a plurality of bit lines, and a plurality of word lines. During programming the memory, a column of memory cells is selected. A voltage difference is respectively occurred between a bit line corresponding to first source/drain regions of the memory cells in the selected column and adjacent two bit lines, and a bias is respectively applied to a word line corresponding to a control gate of each memory cell in the selected column so as to allow a data bit of the memory cell at a plurality of predetermined programmed states and an unusable bit of each memory cell in an adjacent column which shares the same bit line with the selected column at an unusable state.