PURPOSE: To secure an accurate prescribed moisture value for full amount of the dried grain as well as to realize the mass production of the dried grain by installing the correction device which extracts properly the grain under the tempering drying process to measure the moisture and then corrects the error caused through the measurement with the predictive value.

CONSTITUTION: The electric signal detected by moisture detector 13 is supplied to one end of the input terminal of adder 22 in correction device, and the predictive value obtained by giving a precision calculation to the error is supplied to the other end via correcting variable setter 23. And the output signal corrected by adder 22 is supplied to one end of the input terminal of comparator 29 as well as to the display unit through amplifier 26. Comparator 29 supplies the finished moisture value from the other end of he input terminal and via finished value variable setter 28 for the mutual comparison. And relay R is excited by the coincidence signal transmitted from the output side. Relay R opens the contact to stop the rotation of the motor as well as the lubrication to heat generator 2, thus completing the drying function. In such way, the grain can be dried up to the prescribed moisture in an accurate way, at the same time realizing the mass production of the dried grain.