Abstract: An air bubble removal cap includes: a main body portion that is formed in a tubular shape and defines a hollow portion inside, the hollow portion being configured to communicate with a collection tube that accommodates a body fluid from a living body; a connection portion that is located on a proximal side of the hollow portion and to which the collection tube is connectable; an exhaust portion that is located on a distal side of the hollow portion and is configured to discharge gas discharged from the collection tube; a filter that is disposed in the hollow portion and divides the exhaust portion and the connection portion; and a scattering prevention mechanism that covers a proximal side of the filter and prevents the body fluid from scattering to the filter.