The invention discloses a grain drying device. The grain drying device comprises a cyclone cap, a cyclone bin, a bin cap, a drying bin, support legs and an air gathering port; the drying bin is supported through the support legs; the bin cap is arranged above the drying bin; the cyclone bin is arranged above the bin cap; the cyclone cap is mounted above the cyclone bin; the air gathering port is formed in the lower part of the drying bin; the drying bin is used for storing grains; and air enters the drying bin by the air gathering port, and leaves from the cyclone cap by the cyclone bin to form a chimney effect to upwards extract air in the drying bin so as to achieve the purpose of drying the grains in the drying bin. The drying bin is provided with multiple ventilation holes; a fan is arranged in the cyclone bin, is connected with the cyclone cap at the top of the cyclone bin through a fan shaft, and is driven to rotate through the cyclone cap to accelerate upward flowing of the airin the drying bin; and the air gathering port is designed as a horn form, so that the air gathering quantity is increased, the flowing speed of the air entering the drying bin is accelerated, and thedrying efficiency is improved.