A packaging box includes a box body having a bottom board, side boards, and bending flaps; and a cushioning material having a bottom surface section and side surface sections. A restrainer is formed at least one of the bending flaps, the restrainer having a portion that is separated from and opposes the bottom board when the portion of the restrainer is bent into an accommodation space of the box body. A restrain portion is formed at the side surface section of the cushioning material opposing the restrainer formed at the at least one of the bending flaps, the restrain portion having a portion that is positioned at a side of the bottom board so as to abut upon the portion of the restrainer and that opposes the portion of the restrainer when the cushioning material is fitted in the accommodation space of the box body.