For improving heating uniformity we propose a 3-kWatt 2.45GHz microwave dryer using multiple multi-slotted waveguides with the horizontal and vertical array slots. Microwave source of each 2.45GHz magnetron is controlled to improve heating uniformity. The proposed dryer consists of two waveguide with the horizontal slots and one waveguide with the vertical slots. The input power was optimized for improved uniformity of temperature. The optimized power applied to each waveguide. Compared with the conventional microwave dryer, the proposed microwave dryer has improved the heating uniformity up to approximately 55%.