A sheath of a catheter for image diagnosis includes a first filter placed in a first communication hole, allowing a flow of gas to an outside from an inside of a lumen via the first communication hole, and restricting a flow of a component scattering or absorbing light contained in a body fluid to the inside from the outside of the lumen and a second filter placed in a second communication hole, allowing a flow of a liquid component contained in the body fluid to the inside from the outside of the lumen via the second communication hole, and restricting a flow of the component scattering or absorbing the light to the inside from the outside of the lumen.
