The thermal structure of lunar craters has been examined to reveal surface temperature and heat flux in the underground by taking account of radiation heat transfer between internal surfaces of crater wall. The boundary condition is formulated to be integro-differential equation for the radiant exchanges. Analytical results have illustrated that the temperature of crater wall is generally the same or rather lower compared with surrounding plain surface in comparatively lower altitude area and also disclosed that the prominent high temperature is yielded in the polar region due the cosine of incident radiation and the dominant annual cycle of heating.