The invention provides a hydraulic impact hammer device added on a hard rock heading machine and a hard rock heading method and belongs to the technical field of hard rock heading. The hydraulic impact hammer device added on the hard rock heading machine and the hard rock heading method can be suitable for heading operation of large-section full hard rock and half rock roadway, have small structural strength on a roadway surrounding rock layer and can further improve heading and cutting efficiency. The hydraulic impact hammer device comprises a hammer, a hammer handle, a hydraulic cylinder and a connecting seat, wherein the hammer is fixedly connected with the hammer handle, the hammer handle is connected with one end of the hydraulic cylinder, and the other end of the hydraulic cylinder is connected with the connecting seat. The hard rock heading method used by being matched with the hydraulic impact hammer device and a hobbing cutter type cutting head of the hard rock heading machine comprises the steps of utilizing the hobbing cutter type cutting head to cut a rock body to form a cutting groove; enabling the hobbing cutter type cutting head to retreat back to the position away from the rock body after the groove cutting is finished; starting the hydraulic impact hammer device; enabling the hammer of the hydraulic impact hammer device to be close to the edge of cutting groove till the hydraulic impact hammer device touches the rock body, and using the hammer to hammer the rock body till the rock body breaks.