A gusset bag (10) has a pair of opposed planar portions (11, 11) and a pair of opposed side portions (12, 12) which are tucked inwardly. The gusset bag has sealed side edge portions (13) where the planar portions and the side portions are heat-sealed at the respective side edges, and tucked portions (13c) where the entirety or a part in the width direction of the sealed side edge portions is tucked toward the planar portion side or side portion side. The gusset bag and a gusset bag (1) with a mouth member have an excellent freestanding ability and there is little pain associated with the manual squeezing of the gusset bag.