In nano scale, thermodynamic properties of gases show difference from those in macro scales. One of the reasons of this difference is the quantum size effects (QSE), which become significant when compared with the thermal de Broglie wavelength of particles to the characteristic length of the system. In this study, thermodynamic behavior of a photon gas confined in a nanoscale domain is examined in terms of QSE. It is obtained that due to quantum size effects the global thermodynamic properties of a photon gas confined in a nano scale domain are different than those in macro scale. The matter of QSE on thermodynamics of substances at micro/nano scale is relatively a new research area and the new findings might lead to significant new applications.