AUXILIARY STORAGE BOX

An auxiliary storage box is stored inside a storage box including a box body and a lid body and is detachable from the storage box. The auxiliary storage box includes: an auxiliary box body; an auxiliary lid body; and a lid receiving portion. The auxiliary box body is detachable and stored inside the box body. The auxiliary lid body is detachably held on a back surface side of the lid body in such a manner that a first surface faces the auxiliary box body. The auxiliary lid body closes an opening of the auxiliary box body when the lid body closes the box body. The lid receiving portion is disposed in the opening in an upper portion of the auxiliary box body. The first surface of the auxiliary lid body elastically contacts the lid receiving portion to seal the opening when the auxiliary lid body closes the opening.