To enable the cap to be always fitted snugly on the handle, to provide the cap with a sufficient holding force, to retain a brush safely and hygienically without deforming or damaging it, and to facilitate the attaching/detaching operation naturally and smoothly.

In an inter-tooth brush in which a brush part (c) is attached to the bent tip end (b) of a handle (a) bent at an angle crossing the axial line of the handle, a nearly U-shaped receiving part 2 for the handle neck is provided roughly orthogonally on the opening end side of a tubular storing part 1 in which the brush part (c) of the inter-tooth brush is fitted. In this case, the space between the oppositely facing side walls of the handle neck receiving part 2 is made smaller than the neck width of the handle; consequently, with a cap 4 fitted on the handle (a), an engaging rib 3 comes into contact with the handle neck, thereby holding the brush at a prescribed position in the cap 4 without positional deviation nor slipped detachment, and protecting the brush safely.