PURPOSE: To provide a base rock excavator and a base rock excavating chisel with small size and light weight and further with powerfulness,whereby work for excavating a base rock in a mountain district can be efficiently and safely performed.

CONSTITUTION: In an excavator 1, a hydraulic cylinder 28 having a ram 10, dropped down in a frame 29, in the lower part is provided in the upper part inside of the frame 29. In the frame 29, a plurality of telescopically movable legs 4 and arms 5 are removably provided in the outside. A cap 9 having cushions 12, 13 in the upper surface is provided in the bottom part inside of the frame 29 and connected thereto by wire ropes 11. In a chisel 8, its excavating part is formed in a tapered shape, and a tapered part is formed longer than a maximum diameter of the chisel. The excavator 1 is fixed to a predetermined position of a hole 3 by the legs 4 and the arms 5. The ram 10 is lifted by the hydraulic cylinder and dropped down to the cushion 13 in the upper surface of the cap 9. Striking force by dropping down the ram 10 is transmitted to the chisel 8 to crush a base rock.