To provide a fluid waste processing bag in which a fluid such as urine is not leaked from a gas-permeable filter to the outside of the fluid waste processing bag.

In the fluid waste processing bag provided with a main body of the bag surrounded with a soft sheet and having an opening on the upper part of a lateral side, a chamber formed from a hard material and having a fluid lead-in port, a first gas-permeable filter and an opening port and a check valve composed of a first soft sheet and a poured second soft sheet mutually sealed at peripheral edges except for lower ends, the chamber is provided on the outer surface of the main body of the bag at a position where the opening port of the chamber and the opening of the main body of the bag are matched, the check valve is provided on the inner surface of the main body of the bag at a position where the pore of the second sheet and the opening of the main body of the bag are matched, and the first sheet is provided with a second gas-permeable filter to communicate the inside of the check valve and the inside of the main body of the bag.