To dry grains while protecting them against overdry or flaw by detecting relatively undried grains while measuring the moisture in the grains in the way of discharge and discharging only dried grains quickly thereby controlling the drying operation depending on the residual quantity of undried grains and the moisture.

The method for drying grains comprises a step for measuring the moisture of grains dried by a grain dryer in the way of discharge every predetermined time, a step for making a switch from discharge operation to circulatory ventilating operation upon detecting a grain moisture exceeding a finish moisture by a moisture width determined arbitrarily, and a step for making a switch to discharge operation upon detecting a grain moisture within an arbitrarily determined moisture width from the finish moisture by a first specified number of times continuously after switching is made to circulatory ventilating operation.