To provide an interdentium brush which has an enhanced flexural strength and rigidity and reduces the diameter of the inserted part at the same time to be suitable for a narrow interdentium gap, improves the fatigue strength and has an enhanced clutching force on filaments of the brush.

A clutching body K, which clutches numerous filaments 2 and fixes them by twisting, has a structure of two parallel wires 3 and 3 which are double-folded. Because the base Ka of the body K is given at least 55% of an effective cross-sectional area ratio of the wires to the cross-sectional area of the circumscribed circle of a diameter D, the flexural strength and rigidity of the inserted body can be enhanced. Furthermore, because the filaments and the wires has two contact points, the clutching force on the filaments is significantly improved and, therefore, the filament fall-off is prevented.