To provide an image processor with which the amount of rendering can be reduced. A plurality of primitives are categorized into a first group of primitives that are to be displayed on a display and a second group of primitives that are not to be displayed thereon, by an XYZ clipping section, a Z testing section, and a stencil testing section, according to the data about the plurality of primitives in a primitive buffer. A two-dimensional image is drawn in a frame buffer using the data for the first group of primitives in the primitive buffer.