A packaging container for containing an object includes a substantially square-shaped first sheet member and a substantially square-shaped second sheet member overlaid on one another and forming four sides. At least one of the four sides forms an opening from which the object can be inserted. The packaging container also includes a first flap adjacent to the first sheet member through a first fold line at the opening, including a first cover piece to cover one half of the opening when folded, and a second flap adjacent to the second sheet member through a second fold line at the opening, including a second cover piece to cover another half of the opening when folded. The first flap and the second flap are provided at the opening so as not to overlap each other, and the first cover piece and the second cover piece cover substantially all the opening when folded.