This paper describes a thermal resistance measurement of pre-impregnated composite fibers (prepregs) in printed circuit boards (PCBs). To miniaturize electrical devices, electrical components are now embedded in multilayered PCBs and covered with multilayered prepregs made of glass fibers and epoxy resin. To estimate the accurate temperature of the components embedded in the prepreg, we should clarify the thermal contact resistance between prepreg layers around the components. In this study, we measured thermal contact resistance between prepreg layers and discussed the impact of the thermal contact resistance on estimation of temperature of the component.