The invention belongs to the mechanical field, and relates to a method for converting rotary motion into reciprocating impact motion especially suitable for the mining field or the engineering machinery field, and also an apparatus for converting rotary motion into reciprocating impact motion by using the method. The apparatus comprises a machine body, a walking part, and a reciprocating impact part; the reciprocating impact part comprises an impact driving mechanism, a rocker arm, and an impact head; the impact driving mechanism comprises an impact power source member, a transmission part, and a crankshaft; the transmission part comprises a power gear, and a transmission gear; the impact power source member comprises a power take-off shaft; the power take-off shaft is disposed perpendicular to the rocker arm and parallel to the transmission shaft and the crankshaft to allow the transmission gear to drive the crankshaft so as to convert rotary motion into reciprocating motion, or the power take-off shaft is disposed parallel to the rocker arm to change the power direction through a power bevel gear and a transmission bevel gear and then to drive the crankshaft so as to convert rotary motion into reciprocating motion; the crankshaft drives the impact head to perform reciprocating impact; the machine body drives the reciprocating impact part to move for continuous work. The apparatus is high in structure strength, high in efficiency, and long in service life.