To prevent the occurrence of damaged grains as a result of soybeans being charged in a container such as a storage drying container or as tank and effecting a flow of soybeans being accumulated on a ventilation floor and effect drying without using a dehumidifying type constant humidity regulating device and a humidifier, using a large amount of powers.

In a soybean drying method where soybeans are charged in a bin 2 and accumulated on a ventilation floor 21, the atmosphere is supplied in a cooling air duct (a) formed on the under surface side of the ventilation floor 21 by a blower 3, and is blown to above through an accumulation layer G of soybeans on the ventilation floor 21, air blown through the accumulation layer G is mixed in feed air supplied to the cooling air duct (a) through an air duct 7. By regulating a mixture ratio, humidity of supply air is regulated to humidity suitable for drying at a drying speed at which dry and skin cracking are prevented from occurring to soybeans grains.