To provide an easy-to-use device capable of thinning hair strands.

In one longitudinal end portion of the main body 2, there is provided a bristle-planted base portion 3a, a fixed blade and movable blade overlapped to make sliding contact with each other as a plurality of comb-shaped blades, and a thinning member 14 provided to cover the edges of the comb-shaped blades, the thinning member 14 having a plurality of apertures 15, so that hair strands introduced into the space between the blades via the apertures 15 can be thinned. An opening-and-closing member 8 is provided to open and close the apertures 15. When the hair brush 1 is used for the sole purpose of brushing the hair without having to thin the hair, the apertures 15 of the thinning member 14 are closed by the opening-and-closing member 8. This makes it possible to smoothly move the hair brush 1.