An impact testing apparatus for includes a workbench, a bracket defining a vertical passage, a hammer slidably received in the passage of the bracket, a fastening mechanism slidably mounted to the bracket and an anvil for supporting a workpiece to be tested. The workbench includes a horizontal platform. The bracket is arranged over the platform. The fastening mechanism is configured to be selectively fixed to different heights of the bracket relative to the platform, and includes a retaining member capable of being biased between a fist position to hold the hammer and a second position to release the hammer. The anvil is disposed on the platform and aligns with the hammer.