PURPOSE: To prevent dew condensation generated in feeding low-temperature storage grains by required amount.

CONSTITUTION: Grains stored in a low-temperature storage tank 1 in a low temperature state are fed to a preparation device 6 for the next process while discharging a prescribed amount of grains to carry out preparation treatment such as hulling and sorting, etc., and introduced air set to prescribed temperature and humidity conditions is made to act on temporarily stored grains after hulling treatment and grains in a drying tank so as to raise grain temperature in a temporary storage tank and the drying tank, in order to carry out the preparing treatments of hulling and sorting.