Generally, in the laser marking, surface roughness or grooves produced by laser irradiation are utilized for distinction; however, it is hard to distinguish the marked characters or symbols clearly. In this report, the laser marking of IC plastic package making use of the change in color has been described. By this marking method, the characters and symbols marked can be distinguished clearly. Effects of laser irradiation conditions for the change in color are studied, and the laser marking experiment of IC package, which consists of SiO2 powder, carbon black and epoxy resin matrix is conducted. Occurrence of the change in color is controlled by varying irradiation power, irradiation time and irradiation atmosphere. It is found that the change in color occurs under the suitable energy power density, and the O2 gas has the effect on shortening the irradiation time until the change in color occurs. The mechanism of the change in color can be explained as follows : after epoxy resin matrix and carbon black are removed, SiO2 powder is melted by laser irradiation; SiO2 powder which includes many pores are sintered; this sintered SiO2 changes the color from black to white by diffused reflection. These phenomena can be applied to laser marking of IC package for subtle distinction.