<p>A core bit (1) for a core drill allowing a tube (20) to be detachable from a coupling (10) and allowing a core remaining in the tube (20) to be easily removed from the opening of the tube (20) on the segment-free side after drilling, wherein the tube (20) is rigidly fitted to the coupling (10). The coupling (10) of the core bit (1) fitted to the core drill comprises an insert part (11b) allowing the tube (20) to be detachably inserted thereonto. A coupling cover (30) covering the insert part (11b) of the coupling (10) is installed on the outside of the coupling (10). A rotation preventing structure preventing the tube (20) inserted onto the insert part (11b) from being rotated relative to the insert part (11b) and a fixing structure preventing the tube (20) from coming out of the insert part (11b) are provided at different positions.</p>
