To provide a synthetic resin bag making body manufactured by utilizing a weldable face of an olefin resin sheet generating little harmful substances when being burnt.

A synthetic resin bag manufacturing body 1 is formed of a first hollow body 2 and a second hollow body 3. The first hollow body 2 and the second hollow body 3 are formed of olefin resin sheets 5-8 so surface treated as to be printed on one faces 5a-8a. The first hollow body 2 and the second hollow body 3 are formed into the bag shape with one faces 5a-8a set on the front side. The other face 5b of the peripheral edge 5e of a first opening 5d of the first hollow body 2 is heat welded with the faces 7b and 8b of the peripheral edges 7e and 8e of the second opening 7d of the second hollow body 3.