PURPOSE: To prevent the overflowing of contents of a bag when it is released by effecting a single closing action of the bag in the case of failed detection of the bag opening action.

CONSTITUTION: Upon resumption of the bag filling operation with the power source on after the discharge action of grains into an unhulled rice bag 2 has stopped in the process of bag filling operation with the power source off, the unhulled rice bag 2 has already been opened and, therefore, fork sensors S3 and S4 will not turn on even after the lapse of a predetermined time. In the case of the first unhulled rice bag 2 with a counter examined for operating conditions and with the power source on, a chain motor M1 is reversely rotated and an actuator 52 engages with a hand 24 to close the unhulled rice bag 2. The failure of the fork sensors S3 and S4 to turn on when the bag is not the first one after turning on the power source is judged attributable to fitting of the log 2 onto fork shafts 41 and 42 with its opening portion remaining closed, and the bag filling operation is returned to the beginning.