The cleaning device (100) has fastening modules (5,6) for detachably fastening medical instrument (60) and container (7) for receiving liquid (80) and/or air (81). The liquid can be flushed out of container through cleaning device cavity (13,16,25) into instrument cavity (62), when the device is in first operating position. The air can be flushed out of environment through container and cleaning device cavity into instrument cavity, when the device is in second operating position. The liquid is composed of components such as oil, short-chain alcohols and phosphoric acid. An independent claim is included for method for cleaning medical instruments.