PURPOSE: To prevent the crimp of an opening part at a time of attachment to an automatic packer, generation of a pinhole in a bag bottom and damage thereof by applying side seals to both ends in addition to a cross-sectional seal for tubular material and thereafter cutting the tube in a line connecting both side seals to form a baglike article.

CONSTITUTION: Bottom side seals S12a, S12b extending in the longitudinal direction are applied to both ends of the bottom seal of a heat sealing tube 1 in width of 0.5-5% of tube width and in length of 1.5 or more times of longitudinal width of the cross-sectional seal ST12. The side seals S01a, S01b of an opening part are applied to both edges of the opening part of a bag in length of 1.5 or more times of the width of the cross-sectional seal ST12 and in width of 0.5-5% of the tube width. The side seals S01a, S01b having the circular-arclike lower edges are formed in both edges of the opening part of the bag by cutting them. Further a bag 3 is obtained which is equipped with a deformed H-shape seal constituted of the cross-sectional seal ST12 and the side seals S4a, S4b and long triangular side seals S3a, S3b of both edges of the opening part.