To provide a drying method involved in treating food residues and comprising bringing the water content of the residues to ≤10 wt.% in a short time without causing scorching while putting the oxidative deterioration of the oily component of the residues to a minimum, and to provide a small-sized dryer enabling the method to be accomplished.

This drying method comprises the following process: food residues are finely cut or ground and then continuously irradiated with far- infrared rays with the main wavelengths of 4 μm (irradiated surface temperature of 450°C) to 6.5 μm (irradiated surface temperature of 173°C) while renewing the surface of the cut or ground food residues by an appropriate means.