In thermal design of mechanical and electronic equipment with increasing complexity, it is important to estimate thermal contact resistance correctly. In the present study, photo-acoustic method (PAM) is applied, with the aid of theoretical considerations, to the measurements of thermal contact resistance between solids. PAM is one of the non-contact and non-destructive methods for detecting thermal properties of various materials. This method is used to extract thermal contact resistance from the data of maximum phase delay of thermal response to periodically modulated irradiation light. For comparisons, steady-state method with constant heat flux is also performed. The results of both methods show the similar tendency and the same order values.