To improve the attenuation coefficient of the GFRP, it was considered a way to complex with rubber which has high attenuation coefficient. Although the attenuation coefficient is improved by sandwiching the rubber sheet to the GFRP, the strength is lowered. Also, there is a problem in the adhesion between the rubber sheet and the GFRP. In order to solve these problems, it was thought that the holes in the rubber sheet. Test pieces which have different diameters of holes and the width of the rubber were made. And, test pieces were resonated by the vibrator in order to determine the attenuation coefficient by a half-width method. The results of the experiment, to improve adhesion by drilling, it was found to suppress the decrease in strength. Also, when the rubber was sandwiched in GFRP, attenuation coefficient was improved. The diameter of the hole drilled in the rubber changing the vibration damping property.