The distal end portion of an insertion device is fitted into the cylindrical, hollow main body of the washing instrument. A plurality of washing ports are disposed separately from each other on the inner surface of the washing instrument main body. Washing liquids are ejected from the washing ports to a swing base at the distal end portion and its periphery in different directions for washing. When the distal end portion is detached, washing water is sprayed over a shielding wall surface, which is part of the inner surface of the washing instrument main body, to reduce the momentum of the washing liquids and thus prevent the liquids from splashing to the outside.
