A sewing data forming device for sewing machines comprising a coordinate input unit for inputting a coordinate value and a plurality of switches for providing instructions at an operating step, and forming needle position data for the sewing machine by calculating coordinate values sequentially inputted from said coordinate input unit. When needle position data to be newly inputted is within a predetermined distance from previously inputted needle position data, the needle position data to be newly inputted is replaced, when inputted, by the previously inputted needle position data as the same data. Also, a method of forming sewing data for a sewing machine is performed using the above device.