<p>The disclosed bag includes: an opening formed by sealing a zipper onto the respective upper edge sections of two sheets of main-body films; a bottom seal section that is broader in width than the opening; a first side-seal section formed from the bottom seal section up to one end of the opening; a second side-seal section formed from the bottom seal section up to a position lower than the upper end of the first side-seal section; a corner section formed by cutting away the two sheets of main-body films from the upper end of the second side-seal section into a shape that projects inwardly at an acute angle; a third side-seal section formed along the corner section from the upper end of the second side-seal section up to the other end of the opening; and a steam-passage section that is provided at least in the vicinity of the tip of the corner section within the third side-seal section and that is sealed at a sealing strength smaller than the internal fitting strength of the zipper.</p>
