Damage to a packing device and a packed object caused by a load is prevented, and a box and the packed object are protected stably. A box of the packing device includes side surface portions, upper flaps, lower flaps, a protrusion, a fixing portion, and interior cushions. The protrusion is formed by folding part of an upper flap. The fixing portion fixes the protrusion such that the protrusion projects from the upper flap. In a state where an object is accommodated in the box, the protrusion is interposed between the upper flap and the packed object, and disperses the load applied to the box.