A pouring member includes an unsealing cap and at least two rotation prevention sections extending vertically and downwardly from an end surface of an open end side of the unsealing cap and is arranged such that the at least two rotation prevention sections are apart from one another by an angle which is larger than a rotation angle required for twisting off the sealing part, and symmetrically with respect to the central axis of the unsealing cap. A recess is formed such that the recess opens to a front end side of the rotation prevention section, and an engagement projection engages the recess in a direction substantially parallel with a direction in which the rotation prevention sections are extended vertically and downwardly, and is formed at a specific position of the flange part of the pouring member.