Devices and methods for keeping an internal cavity of an implant or specifically an internal cavity provided in a fixture constituting an implant in a clean state by a simple operation without injuring the gingiva around the fixture is provided. A brush for cleaning the inside of an implant provided with a twisted brush part in which helical brush bristles are formed around the wire rod by arranging a large number of resin fibers in parallel in a direction perpendicular to a wire rod and then, by twisting the wire rod, an intermediate columnar part to which the twisted brush part is fixed, and a main columnar part to which the intermediate columnar part is fixed, where a length in a major axis direction of the intermediate columnar part is within a range of 0.8 to 2.0, assuming that a length in a major axis direction of the twisted brush part is 1.