Summary: This paper proposed that a path loss model for outdoor-to-indoor corridor is presented to construct next generation mobile communication systems. The proposed model covers the frequency range of millimeter wave bands up to 40GHz and provides three dimensional incident angle characteristics. Analysis of path loss characteristics is conducted by ray tracing. We clarify that the paths reflected multiple times between the external walls of buildings and then diffracted into one of the buildings are dominant. Moreover, we also clarify how the paths affect the path loss dependence on frequency and three dimensional incident angle. Therefore, by taking these dependencies into consideration, the proposed model decreases the root mean square errors of prediction results to within about 2 to 6dB in bands up to 40GHz.