A simple testing method for mechanical properties of materials in high-pressure hydrogen environments has been developed. This method does not require any high-pressure vessel but the high-pressure hydrogen environment is produced inside the hole in the specimen. The specimen temperature is easily controlled by outside environment. The effects of hydrogen environment embrittlement (HEE) for SUS304 and 304L at 298, 190, and 77 K were evaluated by the ratio of reduction of area obtained in tensile tests in hydrogen to that obtained in helium. The results of the evaluation by this testing method agreed fairly well with the results by the usual method using a high pressure vessel. The hole in the specimen was machined by electric discharge, wire-cut, and honing. The influence of surface roughness on HEE was compared among these processes and the wire-cut machining was found to be enough for this new method. Changes of HEE with temperature and fracture surface by hydrogen proved the usefulness of this new simple method.