A cushioning material interposed between an article to be packaged and a packaging box that houses the article to be packaged, comprising: a first support piece having a first support face and a first inner face, the first support face supporting one face of the article to be packaged; and a second support piece having a second support face and a second inner face, the second support face supporting another face adjacent to the one face of the article to be packaged, wherein the second inner face is linked to the first inner face via a hinge, wherein the first support face projects upward from the first inner face and the second support face projects upward from the econd inner face, when the cushioning material is in the unfolded state, wherein the cushioning material is disposed at each of four corners of the packaging box along a folded side of the packaging box, characterized in that: the second support face projects a predetermined height from the second inner surface; a second projection which projects from the inner face higher than the second support face is disposed between the second supporting face and the hinge; the first support face is equipped with a first cavity which is surrounded by a wall projecting a predetermined height from the inner surface, the first cavity being inserted with the second projection of the second support piece when the first support piece and the second support piece are folded at the hinge; the second projection of the second support piece which is inserted in the first cavity of the first support piece and the first support face of the first support piece are configured to support the one face of the article to be packaged; and the second projection which contacts with the one face of the article to be packaged holds the second support piece folded. a first support piece having a first support face and a first inner face, the first support face supporting one face of the article to be packaged; and a second support piece having a second support face and a second inner face, the second support face supporting another face adjacent to the one face of the article to be packaged, wherein the second inner face is linked to the first inner face via a hinge, wherein the first support face projects upward from the first inner face and the second support face projects upward from the econd inner face, when the cushioning material is in the unfolded state, wherein the cushioning material is disposed at each of four corners of the packaging box along a folded side of the packaging box, characterized in that: the second support face projects a predetermined height from the second inner surface; a second projection which projects from the inner face higher than the second support face is disposed between the second supporting face and the hinge; the first support face is equipped with a first cavity which is surrounded by a wall projecting a predetermined height from the inner surface, the first cavity being inserted with the second projection of the second support piece when the first support piece and the second support piece are folded at the hinge; the second projection of the second support piece which is inserted in the first cavity of the first support piece and the first support face of the first support piece are configured to support the one face of the article to be packaged; and the second projection which contacts with the one face of the article to be packaged holds the second support piece folded. the second support face projects a predetermined height from the second inner surface; a second projection which projects from the inner face higher than the second support face is disposed between the second supporting face and the hinge; the first support face is equipped with a first cavity which is surrounded by a wall projecting a predetermined height from the inner surface, the first cavity being inserted with the second projection of the second support piece when the first support piece and the second support piece are folded at the hinge; the second projection of the second support piece which is inserted in the first cavity of the first support piece and the first support face of the first support piece are configured to support the one face of the article to be packaged; and the second projection which contacts with the one face of the article to be packaged holds the second support piece folded.