Abstract: A toothbrush with a laterally oriented head in which a handle and a head are in a T shape, and an overall upper surface of bristles on the head is in an arc shape, wherein the overall upper surface (3a) of the bristles (3) on the head (2) is formed with a curvature radius of approximately 15 mm that is centered on a point of intersection between an axial center (X) of the handle (1) and an undersurface (2a) of the head (2) or on a point of intersection (Y) between the axial center (X) of the handle (1) and an arbitrary line that is parallel to the undersurface (2a) of the head (2) and is between the bristles (3) and the undersurface (2a) The overall upper surface (3a) of the bristles (3) in an arc-shape is inclined toward the handle (1).