The decrease of ductility due to displacement damage and nuclear transmutation damage by 14-MeV neutrons are major problems to be considered in the selection of fusion reactor materials. In this study with reduced activation Fe-18Cr-15Mn steel, the effect of hydrogen on ductility was investigated by using an electrolytic charging method as a simulation for the (n,p) transmutation effect. The state of hydrogen was clarified by internal friction, X-ray and electron microscopy. The hydrogen peak was found and its parameters were estimated as τ0 = 5.8 × 10-13 sec and H = 0.52eV. In this solute state, the work hardening coefficient and uniform ductility decreased as the charging time increased. This effect was discussed from dislocation phenomenological theory.