To provide a filtering bag such as a draining bag and a strainer causing little clogging even when scavenging removing object substances in large quantities.

A constricted part 12 is formed in a halfway part of the bag by restricting an expanding quantity of the filtering bag. Thus, since the removing object substances intensively accumulate in a downstream chamber 9(b) of the constricted part 12, even when scavenging the removing object substances in large quantities, an upstream chamber 9(a) of the constricted part 12 excellently passes a fluid component so that the filtering bag causing little clogging can be obtained.