This paper tries to evaluate the regulatory effects of CO₂ emissions by implementing environmental policies related on automobiles. Japanese Ministry of Transport set up a target of the GHG emission level of transport sector at 2008 to 2012 as 17% increasing level from 1990 level. In order to comply with this target, Ministry of Transport has been introduced two main environmental policies related on automobiles; those are mileage regulation by top runner method and Green taxes. While these two policies are expected to generate synergistic effects to reduction of CO₂ emissions, these policies are also afraid to have possibilities for increasing CO₂ emissions through traffic volumes induced by being decreased automobile use costs. This is called by rebound effect in the field of environment. Hence we evaluate regulatory effects of CO₂ emissions included its rebound effects by applying the dynamic computable general equilibrium (DCGE) model. The model has characteristics of explicit formulation of the automobile related industrial and transport sector's behavior and household travel behavior. With the numerical simulations by this model, we identify reduced volumes of CO₂ by introducing the mileage regulation by top runner method and Green taxes as present policies. The results are that the decreased rate of CO₂ is 6% in 2010. But it is not reach the target of the GHG emission level of transport sector. JEL classification: Q54, Q58