A safe brushing is realized without sticking the gum if the bristle tips are once inserted in a pocket of a tooth by using a system having a brush of which the bristle tips automatically vibrate in a direction at right angles with the direction of length of the bristles. A brush lever 5 having a brush 4 is swingingly supported in the nozzle 1, a flow passage 3 leading to a blow-out port 1a at an end of a nozzle 1 is partly bent, and a resilient member 7 is provided at the bent portion to urge the brush lever 5 in a direction opposite to the direction of flow of water, so that the brush lever 5 oscillates reciprocally due to the resilient force produced by the resilient member 7 and the pressure of water flow, causing the bristle tips of the brush 4 to oscillate in a direction at right angles with the direction of length of the bristles outside the nozzle 1.