To provide a system and method for manufacturing a film case by which light shielding performance at a film discharge outlet can be ensured, and a film case.

A heater 347 is made a concave-convex shape directed to the film discharge hole 20 side. That is, protrusions 347b are formed on both ends of a base portion 347a, a protrusion 347d is formed on the central part of the base portion 347a, and protrusions 347c are formed between each of the protrusions 347b and the protrusion 347d at predetermined intervals. When the heater 347 is pressed on the upper side of a light shielding sheet 22 temporarily stuck to one end 18 of a case body 14, many small creases 412 due to the uneven concave-convex shape are formed in the light shielding sheet 22, accordingly curl and shrinkage of the light shielding sheet 22 or waving of the light shielding sheet 22 due to a local variation in thickness or shape at the one end 18 of the case body 14 can be suppressed.