To provide a gusset bag which prevents load or stress from being concentrated on an intersection of an inclined welded portion of a gusset and a welded portion provided on one side of the bag if a wide article is put in the gusset bag and the widths of the article and the gusset do not match.

The gusset bag made of a thermoplastic synthetic resin film is provided, wherein the inclined welded portion consisting of two films inclined by 45 degrees from a folded end of the bag and welded does not reach a bottom welded portion of the bag, its length is specified to be a half to 75% of a gusset folding depth toward the bottom thermally welded end, and a non-welded part is formed between the inclined welded portion and the welded end.