To seize the condition of the moisture content distribution of grains in a whole grain drying machine and easily actualize adequate drying control by precisely measuring the moisture content of the grains in each of grain layer built up and charged into the grain drying machine.

After completion of charging work for the grains, a charged grain amount setting means 20 sets the charged amount of the grains. Then, a control part 41 calculates a circulation time (t) required for circulating the grains once in accordance with the charged amount set by the charged grain amount setting means 20 and sets a measuring frequency (k) for moisture content measuring work to be done in the circulation time (t) from start of the drying process to completion of the circulation of the grains once.