The invention relates to a drying machine, particularly a supporting device of a roller of a drying machine. The supporting device comprises a pair of supporting rolls used for supporting the lateral faces of the opening part of the roller, a roller spindle and a bearing arranged in the center of the bottom of the roller. A circular protecting hood with M-shaped cross-section is arranged on the outer side of the bottom of the roller and fixed on an outer casing of the drying machine. The circular hood and the bottom of the roller form a ring-shaped air chamber; a plurality of air intake holescommunicating with the ring-shaped air chamber is formed at the bottom of the roller; a through-hole for the roller spindle to pass through is formed on the circular hood; a bearing supporting seat is fixedly arranged on the circular hood; the bearing passes through the circular hood, and is arranged in the bearing supporting seat; and a plurality of cooling ventilation holes are formed on the bearing supporting seat. The supporting device has the advantages of convenient assembly, stable rotation when in use, good heat dissipation of bearing, good safe-grounding performance, and prolonged service life of the drying machine.