To provide a container bag 34 that can be manufactured easily by folding a sheet material 1 precisely along a folding line 11B. The sheet material 1 is prepared by bonding two films 2 and 3 together in a predetermined pattern, and the sheet material 1 comprises a plurality of cells 16 formed between the two films 2 and 3 while being joined to one another to be filled with fluid. A trunk portion 17 to be filled with a content is formed by bonding overlapping layers of a peripheral edge 9A of the folded sheet material 1. A bottom portion 13 of the container bag 34 is folded inwardly toward the trunk portion 17 along the folding line 11B. A non-bonded section 14 in which the two films 2 and 3 are not bonded together is maintained linearly within the folding line 11B.