A sewing data generating unit acquires embroidery frame information and a mark alignment region displayed on a display unit for guiding multiple marks that define an embroidery region of the embroidery frame. When the marks are all positioned within the mark alignment region displayed on the display unit, the sewing data generating apparatus acquires an image of the embroidery frame and a sewing target mounted on a base cloth mounted on the embroidery frame. The sewing data generating apparatus performs image analysis based on a correspondence between the acquired information with respect to the embroidery frame and the marks in the acquired image, so as to determine the embroidery region of the embroidery frame. The sewing data generating apparatus generates outline data for the sewing target based on the determined embroidery region. This allows an applique to be sewn at an accurate position without a need to prepare dedicated data.