JCP(Jointed plain cement Concrete Pavement) is severe affected by environmental load such as temperature, relative humidity. Concrete slab repeatedly shrink and expand due to environmental loading is referred to curling and warping. As a result, restraint stress increases and joint can be damaged. Under the tunnel condition, temperature and relative humidity variations are smaller as compared with outside of the tunnel. Therefore it`s expected that JCP under the tunnel condition is less affected by environmental load than JCP outside of the tunnel. Also Joint opening behavior could be differ JCP of each condition. In this study, air temperature and relative humidity varying distance from entrance of tunnel, temperature by slab depth, and displacement of joint are measured at outside and inside of three tunnels on the expressway, using I-button and VW crackmeter sensor. As expected, difference of joint opening behavior could be evaluated. According to measuring result, design of pavement section and joint spacing of JCP could be determined under the tunnel condition.