To protect against external impact and allow a package itself to be used as a standard-size mail by sectioning a rectangular base material into three approximately equal parts via two creases to provide a surface piece, a rear piece and an intermediate folded piece and by forming a holding part for an object to be packaged on the intermediate folded part.

A rectangular base material 1 is sectioned into three equal parts via creases L1, L2 to provide a center surface piece 10, a rear piece 20 and an intermediate folded piece 30. A breaking line 22 is scored in a gate shape with a first margin 21 of a predetermined width left on the rear piece 20 to provide an opening piece 23 which can be cut to open. A breaking line 32 is scored in a gate shape with a second margin 31 left on the intermediate folded piece 30 to provide a holding part 33 of the object. A receiving window 34 for the object is opened on the holding part 33, and a plurality of flaps 35 are formed along a periphery. Paste is applied on the second margin 31 to stick the intermediate folded piece 30 to overlay it on the surface piece 10. Paste is applied from the holding piece 33 which has become a surface of the intermediate folded piece 30 to the second margin 31, and the object is placed in the receiving window 34. The rear piece 20 is stuck to overlie on the intermediate folded piece 30 to provide a mailing package.