A drilling apparatus, comprising a hammering apparatus built-in the drilling apparatus, the hammering apparatus which comprises a drill head comprising: a weight hammer (7,8); a compression spring for applying a biasing force to the weight hammer; and a rotor (9,10) provided with an engagement claw (9a, 10a) that engages, through rotation thereof, the weight hammer (7,8) to cause the weight hammer to move from an original position thereof to a direction of increasing the biasing force of the compression spring, and that releases the engagement of the weight hammer at a predetermined position, in which through the rotation of the rotor (9,10), the engagement claw (9a, 10a) engages the weight hammer to cause the weight hammer to move to the direction of increasing the biasing force of the compression spring, and releases the engagement of the weight hammer at the predetermined position to cause the weight hammer to move to a direction of the original position with the gravity of the weight hammer and the biasing force of the compression spring, and thus the weight hammer hammers an object to be hammered with a hammering force obtained by adding the biasing force of the compression spring to the gravity of the weight hammer, wherein: the weight hammer comprises a plurality of weight hammer elements (8,7), with at least a first hammer element and a second hammer element; the first and second weight hammer elements (8,7) having portions (15, 19) with respective shape for alternately and substantially evenly applying the hammering force with respect to a surface to be hammered of the object to be hammered, characterized in that the first hammer element has a circular column portion and the second hammer element has a cylindrical portion surrounding the circular column portion along a center line of the object to be hammered and the circular column portion is to be slidable through the cylindrical portion; the rotor comprises a plurality of rotor elements (9,10); the plurality of rotor elements (9,10) for driving the plurality of weight hammer elements (9,10) are provided correspondingly to the plurality of weight hammer elements (9, 10), respectively; the plurality of rotor elements (9, 10) are provided to a same rotating shaft in such a positional relation that an engagement claw (9a, 10a) of one of the plurality of rotor elements (9,10) engages and drives one of the plurality of weight hammer elements (9,10), and, when engagement of the one of the plurality of weight hammer elements (9,10) is released, an engagement claw (9a, 10a) of another of the plurality of rotor elements (9,10) in driving engages another of the plurality of weight hammer elements (9, 10); and the plurality of rotor elements (9, 10) are driven by the same driving means. a weight hammer (7,8); a compression spring for applying a biasing force to the weight hammer; and a rotor (9,10) provided with an engagement claw (9a, 10a) that engages, through rotation thereof, the weight hammer (7,8) to cause the weight hammer to move from an original position thereof to a direction of increasing the biasing force of the compression spring, and that releases the engagement of the weight hammer at a predetermined position, the weight hammer comprises a plurality of weight hammer elements (8,7), with at least a first hammer element and a second hammer element; the first and second weight hammer elements (8,7) having portions (15, 19) with respective shape for alternately and substantially evenly applying the hammering force with respect to a surface to be hammered of the object to be hammered, characterized in that the first hammer element has a circular column portion and the second hammer element has a cylindrical portion surrounding the circular column portion along a center line of the object to be hammered and the circular column portion is to be slidable through the cylindrical portion; the rotor comprises a plurality of rotor elements (9,10); the plurality of rotor elements (9,10) for driving the plurality of weight hammer elements (9,10) are provided correspondingly to the plurality of weight hammer elements (9, 10), respectively; the plurality of rotor elements (9, 10) are provided to a same rotating shaft in such a positional relation that an engagement claw (9a, 10a) of one of the plurality of rotor elements (9,10) engages and drives one of the plurality of weight hammer elements (9,10), and, when engagement of the one of the plurality of weight hammer elements (9,10) is released, an engagement claw (9a, 10a) of another of the plurality of rotor elements (9,10) in driving engages another of the plurality of weight hammer elements (9, 10); and the plurality of rotor elements (9, 10) are driven by the same driving means.