An oral cavity washing device includes a housing, a tubular storage space formed in the housing to store a liquid, and a pump housed in the housing to discharge the liquid. The housing includes a peripheral wall section constituting at least part of a peripheral wall of the storage space and having a supply port for supplying the liquid into the storage space, and a lid disposed at one end of the storage space to be able to entirely open and close a largest opening that is larger in area than any other opening in the housing.
