To provide a medical disposal bag made of plastic film with no shape retaining property, capable of being easily removed after storing a waste liquid from a closed type medical suction appliance, reducing a space of a stock, and surely sucking the waste liquid such as a body fluid to stock the same in the closed type medical suction appliance.

The medical disposal bag 1 set in the closed type medical suction appliance sucking the waste liquid such as the body fluid by sucking with a suction unit to stock the same is made of a plastic composite film and has an air permeability ranging from 50 to 300 (sec/0.1L), wherein the air permeability has been measured according to JIS P8117 using a Gurley Type Densometer. Preferably, the above medical disposal bag has a pair of film walls 2, 3, the whole surface or part of at least one film wall is made of an air permeable plastic film mainly comprising a polyolefin.