TOOTHBRUSH

Provided is a toothbrush with a thin head with which good maneuverability can be obtained. The toothbrush is provided with a head section (110), which is disposed at the tip end and in which bristle bundles are implanted in an implanted bristle surface (111), a neck section (120) extending from the back end of the head section, and a handle section (130) extending from the back end of the neck section. The thickness of the head section is 2.0-4.0 mm. The neck section is formed so that the minimum value for the width in the direction parallel to the implanted bristle surface and orthogonal to the longitudinal direction of the handle section is 3.5 mm to 4.5 mm, and the width is constant or gradually increases towards the back end from the position with the minimum value. When the neck section width is W mm, the thickness in the direction orthogonal to the implanted bristle surface is D mm, and the origin is the position of the minimum value when the neck section width increases gradually towards the back end from the position of the minimum value or the origin is the position of the minimum value closest to the tip end when the neck section width becomes constant towards the back end from the position of the minimum value: the value determined by D/W at the position parallel to the implanted bristle surface and separated 10 mm towards the back end is 0.7 to 2.5; the difference between the value determined by D/W at the position of the origin at which the width is the minimum value and the value determined by D/W at the position separated 20 mm towards the back end from the position of said origin is at least 0.05; D/W for the position separated 20 mm towards the back end from the position of said origin exceeds 1.0; and the deflection coefficient M (mm4)=W×D3 at the position separated 10 mm towards the back end from the position of the origin at which the width is the minimum value is 165 mm4 to 625 mm4.