A sewing data editing device includes a processor and a memory configured to store computer-readable instructions that, when executed by the processor, instruct the processor to perform processes. The processes include acquisition processing of acquiring coordinate data representing a position of each of a plurality of points along a predetermined pattern, corner portion detection processing of detecting, based on the coordinate data, a corner portion having an angle smaller than a predetermined angle, and editing processing of editing sewing data, based on the coordinate data of each of the plurality of points and on a detection result of the corner portion detection processing, using editing conditions that are mutually different for a plurality of first needle drop points corresponding to the corner portion and for a plurality of second needle drop points corresponding to a non-corner portion not detected as the corner portion, in the predetermined pattern.