To provide a film bag which can suppress generation of a curved deformation (a curl) on an opening part and can prevent a bundle made by piling-up a specified number of the film bags from becoming bulky when the film bag prepared by using a laminated cylindrical film or a co-extruded cylindrical film as a raw material, is an object for this purpose.

In the film bag 1 the raw material of which is the co-extruded cylindrical film 1a (or the laminated cylindrical film) flat folded so as to overlap facing film pieces 10 and 10 each other, with the opening part 11 formed on one end, and a bottom part sealed part 12 formed on the other end, a temporarily sealed part 13 in which the facing film pieces each other are releasably temporarily stuck are formed on the opening part 11.