To provide a toothbrush which has a replaceable brush head around a protrusion formed in one end of a handle, where the tip of the brush head is made smaller so that it can be easily moved in one's mouth.

A head body 11 consists of a brush wall 13 on which bristles 12 are implanted, and side walls 15 each having a groove line 18 inside, all of which form an empty space inside. A protruding piece 7 in one end of a handle is provided with a protruding line 8 on each side, through which the individual groove line 18 is fitted when the head body 11 is attached to the protruding piece 7 to cover it. Since the protruding piece 7 is covered with no wall on the opposite side of the brush wall 13, the brush head, the part to be put into a mouth, becomes slim, thinner in depth and less bulky, and therefore it becomes easy to move the toothbrush in the mouth, achieving better sanitary conditions in the mouth.