Vectorization of an image in which a monospaced line and surfaces coexist without generation of a gap in a boundary between the monospaced line and the surfaces or between the surfaces, is realized. Separation processing of the monospaced line and the surface is executed for each color region. After the separation, a pixel position where the monospaced line is located is filled with color information of an adjacent surface. Boundary-sharing type vectorization processing is executed for data which is obtained by filling the monospaced line. Further, vector data expressed by a core line and a line width is generated based on the monospaced line obtained by separation processing of the monospaced line and surface. A vectorization result of the monospaced line extracted according to each color, and a vectorization result of a boundary line of the surface generated from data after a monospaced line region is filled are outputted.