<p>A paper package (9) that is set in a printer has piled sheets of paper (7), and a sheet-like package material (8) folded in a box-like form so as to be able to receive the sheets of paper (7). A first incision (34) is formed in one part (55) of the package material, and a projection portion (35) that is inserted in the first incision (34) to maintain the shape of the package material is formed on the other part (53). The projection portion (35) has a base portion (35n) having a narrower width than the first incision (34) and a wide portion (35w) having a wider width than the first incision (34). Both end portions (34c) of the first incision (34) are curved in a letter 'U' shape. A second incision (34s) is extended from substantially the center of the first incision to the direction of the insertion of the projection portion (35).</p>
