A bag (1) with a chuck tape, wherein the chuck tape (20) having a male type fastener part (21) and a female type fastener part (22) is fitted to one inner surface of a bag body (10), a cut tape (23) is fitted between the mounting base parts (212) and (222) of these fastener parts, and an easily unsealable structure (50) is formed in the mounting base part (212) at the unsealing start part (30) ofthe side seal part (60) of the bag body adjacently to the cut tape (23). To form the easily unsealable structure (50), a hole portion (50a) or a portion formed of a weak line may be formed in the mounting base part (212), the thickness of the mounting base part (212) at the unsealing start part (30) may be reduced less than the thicknesses of the other portions, or a non-adhesive part may be formed between the mounting base part (212) and the cut tape (23).