The technology for sludge drying using a microwave is a primary process in producing solid refuse fuel in the waste-toresource process. In this paper, the drying efficiency is improved by investigating chamber types such as square and circle with various mechanical conditions such as the magnetron power, the height of microwave irradiation, and the sludge thickness. In identical conditions, the moisture content was generally uniform in the circle chamber due to the uniform distribution of microwave irradiation, and the drying efficiency was higher in the circle chamber compared to the square chamber. In the case of the circle chamber, the drying rate was increased by more than 30% and the energy for sludge drying 507.9 kcal/kg of water was reduced. Hence, the application of a circle chamber should save energy consumption in sludge drying.