A device for cleaning oral cavity and a method for cleaning oral cavity capable of cleaning stains such as plaque, tartar, and the like even in a narrow portion such as a clearance between teeth, a clearance between implants, and the like. A cover includes a jetting orifice and a discharge orifice and covers a tooth by leaving a clearance between the tooth and the cover so that the clearance can hold water. A jetting unit is mounted in the jetting orifice and includes a flow path communicating with the clearance between the tooth and the cover. The jetting unit is configured to generate cavitation bubbles. The flow path includes a small diameter part and an enlarged part. A discharge unit discharges water in the clearance between the tooth and the cover from the discharge orifice.
