A bullet-mark information memory unit (250) stores bullet hole information containing a normal map defining a recess of a bullet hole. An original image drawing unit (261) draws an original image containing an object having undergone lighting. A synthesizing unit (262) synthesizes a bullet hole to which a normal map is applied with a hit location of the drawn object. A compensation value calculating unit (263) calculates a compensation value based on a relationship between a normal line of the object and a light source direction. A brightness value calculating unit (264) calculates a brightness value based on a relationship between a normal line direction of a bullet through a normal map and a light source direction, and a relationship with the calculated compensation value. A shading unit (265) uses the calculated brightness value and performs shading which changes a tone of the object at a synthesis position.