A resistive memory device and a sensing margin trimming method are provided. The resistive memory device includes a memory cell array and a trimming circuit. The memory cell array has a plurality of resistive memory cells. The trimming circuit generates a trimming signal according to a characteristic distribution shift value of the resistive memory cells. With the inventive concept, although a characteristic distribution of memory cells is varied, an erroneous read operation is minimized or reduced by securing a sensing margin stably. Accordingly, a fabrication yield of the resistive memory device is bettered.