Provided is a disposable bag in which a feeling of filth is hardly sensed, and which, together with the filth contained in the bag, can be disposed of into drainage water. The disposable bag (1) is configured such that a water-soluble filth collecting member (2) used for collecting filth such as excrement of a dog and a water-soluble filth containing member (3) for containing, together with the filth collecting member, the collected filth are joined together in a separable manner by an approximate linear perforation (5). In the filth collecting member (2), notches (4) for bringing the filth collecting member into a U-shape by engaging with each other at outer edges apart from the perforation (5) are formed. In the vicinity of the perforation (5) of the filth containing member (3), through-holes (6) are formed. The filth collecting member (2) and the filth containing member (3) are kept apart along the perforation (5) and the notches (4) formed in the filth collecting member (2) are engaged with each other to bring the filth collecting member (2) into a U-shape. The filth collecting member (2) thus formed in a U-shape is used to pick up excrement (7) as if to use a scoop.
