A washing system includes a cylindrical body portion which is prepared for each kind of insertion portion and a supply hole portion which is provided in the body portion to communicate with the inside of the body portion and which supplies a fluid to an opening portion of an insertion portion housed in the body portion. The washing system includes a supply mechanism which is shared by the body portion corresponding to each insertion portion that is prepared which supplies the fluid to the supply hole portion and which is attachable to and detachable from the supply hole portion.