This paper explores whether a coal tax can be rationale of exporters in a general equilibrium model. Richter et al. (2018) employs a partial equilibrium model and shows even a unilateral coal export tax can increase social welfare of Australia and contribute to global emissions reduction. However, this general equilibrium analysis shows that the answer depends on the degree of power of coalition to change the world price of coal. In other words, the size of coalition is important. Also, competition of coal with other fossil fuels, nuclear, hydro-power and other technologies is another significant factor to drive the result.