Provided is a casing protection bit mounted on a casing tube in combination with a cutter bit to prevent abrasion or chipping of the cutter bit. The present invention is to provide a casing protection bit 1 to be mounted on a casing tube, the casing protection bit including: a base portion 2 that protrudes in an axial direction of the casing tube, the base portion having a mountain shape; and two leg portions 3 and 4 extending continuously with the base portion 2 and facing each other at a predetermined distance. In the casing protection bit cemented carbide tips 5a to 5j are disposed on all planes of the base portion 2 except for a plane from which the leg portions 3 and 4 extend.