PURPOSE: To maintain the high quality of grains and reduce construction cost.

CONSTITUTION: The outer wall of a building is constituted of a dry storage bin 1 and the same panel P as the panel P of a machine room 2, and the roof 13 of the building is constructed with a tent of double structure. As a result, an air layer is formed in the space 133 of the double structure, thereby enabling a heat-insulation effect to be maintained and the effect of radiation heat due to solar heat to be lessened for maintaining the high quality of grains. In addition, the roof structure itself can be simplified without any addition of a special insulation layer structure, and the outer wall can be simplified to reduce the construction cost of a processing facility for grains.