A belt-like base section (321) of a male member (32) of a fastener tape (3A) attached to the inner surface of a bag body (2) has a body (3211) where an interlocking section (31) is provided, a first rA belt-like base section (321) of a male member (32) of a fastener tape (3A) attached to the inner surface of a bag body (2) has a body (3211) where an interlocking section (31) is provided, a first ridge section (3212) provided on the body (3211) on its opening side, a thin wall section (3213) provided on the first ridge section (3212) on its opening side, and a second ridge section (3214) provididge section (3212) provided on the body (3211) on its opening side, a thin wall section (3213) provided on the first ridge section (3212) on its opening side, and a second ridge section (3214) provided on the thin wall section (3213) on its opening side. A belt-like base section (331) of a female member (33) has a body (3311), a first ridge section (3312), a thin wall section (3313), and a seconded on the thin wall section (3213) on its opening side. A belt-like base section (331) of a female member (33) has a body (3311), a first ridge section (3312), a thin wall section (3313), and a second ridge section (3314). When the fastener tape (3A) is fusion bonded to the bag body (2), a gap is formed between each thin wall section (3213, 3313) and each film of the bag body (2).ridge section (3314). When the fastener tape (3A) is fusion bonded to the bag body (2), a gap is formed between each thin wall section (3213, 3313) and each film of the bag body (2).