There is disclosed a cleaning device which is mounted in a surgical treatment instrument (1) so as to be attachable/detachable and in which a cleaning cover (81) having a shape to surround a distal-end function portion (21) is disposed and includes a jet port (87) opening toward the distal-end function portion (21) of the surgical treatment instrument (1) and which supplies cleaning water into the cleaning cover (81) via the jet port (87) to clean the distal-end function portion of the surgical treatment instrument (1) disposed in the cleaning cover (81). <IMAGE>
