Packing material including cushion

A packing material comprising:

• an outer case allowing a to-be-packed object to be put inside;
• and
• a cushion arranged in a gap between the outer surface of the object and the inner wall of the outer case, including:
• a bag containing gas and hermetically sealed;
• a partition linearly dividing the inside of the bag into first and second rooms of the same capacity;
• and
• a duct connecting between the first and second rooms, wherein
• when the partition is placed along an edge of the object that is shared by first and second outer faces of the object, the cushion can bend at the partition and contact the first outer face of the object at the outer surface of the first room of the bag and the second outer face of the object at the outer surface of the second room of the bag,
• the outer case, when containing the object and the cushion, applies pressure to the outer surfaces of the first and second rooms of the bag through the inner wall contacting the outer surfaces of the first and second rooms, and the pressure includes a first component pressing the first room to the first outer face of the object and a second component pressing the second room to the second outer face of the object, and
• when the outer surface of the first room of the bag receives a force through the outer case from its outside, gas moves from the first room through the duct to the second room against the pressure applied by the outer case to the second room, and when the force from the outside of the outer case is removed, gas returns from the second room through the duct to the first room due to the pressure applied by the outer case to the second room.