High-magnesium Al-Mg alloys are known to be sensitive to stress corrosion cracking involving environmental hydrogen, hydrogen invading from the corrosive environment. In this study, the behavior of the environmental hydrogen in Al-6%Mg and Al-8%Mg binary alloy sheets stretched by 10% during exposure to 3.5%NaCl solution has been investigated by means of hydrogen microprint technique. Microprint image is observed on one surface while the other surface is exposed to the solution. In both alloys, the silver particles corresponding to the sites where hydrogen atoms are emitted from the inside of the sheets are shown on the slip lines. It is shown that the hydrogen atoms are transported with moving dislocations in the alloys.