A memory device and a programming method thereof are provided, and the programming method of the memory device includes following steps. A memory cell grouping procedure is performed to divide a plurality of memory cells into a plurality of groups. After the memory cell grouping procedure is performed, a programming procedure is performed, and the programming procedure includes following steps. A first programming pulse, a second programming pulse and a verification pulse are provided to a word line. A first group is programmed by the first programming pulse, and a second group is programmed by the second programming pulse. Whether the first group and the second group respectively pass a verification operation is determined by the verification pulse.