Abstract: A core drill of dry type used for drilling through concrete structure or the like. A main shaft 23 rotatably driven by a motor 33 with a fan 32 is provided with a rubber ring 27 for allowing axial vibration of the shaft, and loosely supported by bearings 25 and 26 with a clearance between them so that it can be slightly tilted in the lateral and transverse directions. During drilling, a spacing between a diamond tip in a leading end of the core bit and a concrete structure or the like is changed as the core bit is moved in the vertical direction and tilted in the lateral and transverse direction, and chips produced by the drilling operation are efficiently discharged by injecting air from the fan 32 through an axial bore 22 in the shaft 23.