A pouch comprising: a bag body including an internal space for accommodating a content; an opening formed in the bag body and communicating the internal space to an outside of the pouch; and a fastener configured to open and close the opening, wherein the fastener having a length LA includes a high engaging-strength portion and at least one low engaging-strength portion having a length LD, the high engaging-strength portion has a first section having a length LB, and a second section having a length LC, and one of the at least one low engaging-strength portion is positioned between the first section and the second section of the high engaging-strength portion, the following equation is satisfied LA = LB + LC + LD such that LD is in a range of 0.05 to 0.7 of LA, the engaging strength of the low engaging-strength portion is less than the engaging strength of the high engaging-strength portion, the fastener includes a female track (1110; 1210) and a male track (1150, 1160; 1250), the high engaging-strength portion includes a female track base, a normal female track, a male track base and a normal male track, the normal female track is shaped like a bowl and the normal male track is shaped like an arrowhead, the low engaging-strength portion includes a female track base, a deformable female track, a male track base and a deformable male track base, the engaging strength of the at least one low engaging-strength portion is selected to be equal or less than 90% of the engaging strength of the high engaging-strength portion, and the low engaging-strength portion is formed by collapsing the fastener having the same configuration as the high engaging-strength portion under a predetermined pressure, a predetermined time, and a predetermined temperature. a bag body including an internal space for accommodating a content; an opening formed in the bag body and communicating the internal space to an outside of the pouch; and a fastener configured to open and close the opening, wherein the fastener having a length LA includes a high engaging-strength portion and at least one low engaging-strength portion having a length LD, the high engaging-strength portion has a first section having a length LB, and a second section having a length LC, and one of the at least one low engaging-strength portion is positioned between the first section and the second section of the high engaging-strength portion, the following equation is satisfied LA = LB + LC + LD such that LD is in a range of 0.05 to 0.7 of LA, the engaging strength of the low engaging-strength portion is less than the engaging strength of the high engaging-strength portion, the fastener includes a female track (1110; 1210) and a male track (1150, 1160; 1250), the high engaging-strength portion includes a female track base, a normal female track, a male track base and a normal male track, the normal female track is shaped like a bowl and the normal male track is shaped like an arrowhead, the low engaging-strength portion includes a female track base, a deformable female track, a male track base and a deformable male track base, the engaging strength of the at least one low engaging-strength portion is selected to be equal or less than 90% of the engaging strength of the high engaging-strength portion, and the low engaging-strength portion is formed by collapsing the fastener having the same configuration as the high engaging-strength portion under a predetermined pressure, a predetermined time, and a predetermined temperature.