The kinetics of drying of a dense buckwheat layer in a microwave electromagnetic field of frequency 2.45 GHz has been investigated for different amounts of the material charged into a working chamber. Analysis of the kinetics curves has shown that the drying of the material studied is divided into the periods of heating, drying with a constant rate, and drying with a decreasing rate. The influence of the power supplied as well as the mass and dimensions of a sample on the rate of its drying has been investigated and a formula for calculating this rate has been obtained. It has been established that, in the process of drying of a disperse material, the amount of microwave energy converted into heat energy depends not only on the mass of a sample, but also on the thickness and area of its surface layer. Generalized equations for calculating the moisture content in a layer of a free-flowing material and its temperature have been obtained.