To provide an interdental brush which demonstrates a function for effectively cleaning a periodontal part and an interdental part by simple constitution.

The interdental brush includes: a brush body 2 in which a base end part is formed by welding many filaments 2a made of resin and trimmed in a required length at one end; and a holding body 3 of a required length for receiving and holding the brush body 2 inside. The proximal end part 2b of the brush body 2 is moved forward and backward on the outer side of the rear end part of the holding body 3 and thereby the function of the brush by the setting of the projecting length of a brush end part from the end opening 4 of the holding body 3 is changed.