To provide a toothbrush which ensures reliability in unification by adopting a preventive structure against the brush head being pulled off.

This toothbrush comprises a brush handle 40 and a brush head 50 that can be replaced and detachably attached to the neck of the brush handle 40. The brush handle 40, squarely hollowed in the neck side to form an insertion hole 41, is provided with a stopper clearance G on one of the square surfaces inside the insertion hole, while the brush head 50 is provided with a stopper nail 51, protruding outwardly from an insertion neck N that is shaped differently in cross section, to engage with the stopper clearance G, as well as a rectangular lump of soft-silicone rubber 52 supported by a protrusion 51 that is integrally formed behind the stopper nail 51. When the insertion neck N of the replacement brush head 50 is inserted into the insertion hole 41 of the brush handle 40, the stopper nail 51 becomes engaged with the stopper clearance G via a nail F3 on the stopper nail 51, where the silicone rubber lump 52 fixed on the rear side of the stopper nail 51 intensifies the engagement because it is also pushed into the insertion hole 41 and therefore serves as an energizer due to the elastic deformation to add the pushing power out of the stopper nail.