A mouth cavity sanitary device comprising: an outer case formed in a cylindrical shape so as to be capable of being held by one hand; an elongated drive unit detachably accommodated in the outer case from a lower portion, the drive unit having a pump thereof disposed in a lower portion of the outer case; a battery detachably accommodated in the outer case from also the lower portion so as to run parallel to the drive unit, the battery being electrically connected to the motor of the drive unit; a reservoir chamber formed from the upper portion of the outer case to the portion in which the drive unit and the battery are respectively accommodated, the reservoir chamber being connected to the suction side of the pump; and a nozzle the base portion of which is detachably fastened to the upper portion of the outer case, the nozzle being connected to the discharge side of the pump.