Crack growth testing is one of the necessary material tests at the high flux test module. It is necessary to develop a small-size specimen in order to measure crack growth. In this study, the effect of hydrogen on the crack growth in F82H steel was investigated through the use of specimens that were one-quarter the size of a standard-size specimen and were cathodically hydrogen charged. A wedge opening load (WOL) specimen was employed for the miniaturized specimen, because the loading mechanism of WOL specimens is quite simple relative to those of other notched-specimen designs. The loading bolt and pin were coated with zirconium oxide film to provide electrical insulation between the WOL specimen and the loading bolt and pin, in order to avoid the formation of a local cell in the water. The hydrogen charging process was conducted for around 600 h in electrolytic solution at a temperature of 35°C with a current density of −2 mA/cm². A constant load with an equivalent initial stress intensity of K = 30 MPa√m was then applied to the specimen for about 337 h at room temperature in air, and the rate of crack growth was measured. Cleavage features were observed on grain facets between the pre-cracking area and the post-cracking area in the hydrogen-charged specimen. It seemed that the feature formed by the crack proceeded by two steps in one grain facet. It is believed that the feature formed is typical of hydrogen embrittlement. Therefore, the small-size specimen used in this study is thought to be a useful one for evaluating the effect of hydrogen on crack behavior in F82H steel.