A programming method of a semiconductor memory device includes, in an n-th program loop, applying a first program pulse to a first memory cell group, applying a second program pulse to a second memory cell group, and determining first fast cells and first slow cells in the first memory cell group, and in an n+1-th program loop, applying a third program pulse, which is increased by a step voltage from the first program pulse, to the first fast cells in the first memory cell group, and applying a fourth program pulse, which is increased by the step voltage from the second program pulse, to the first slow cells in the first memory cell group and the second memory cell group.