Hydrogen-induced defects of AISI 304 stainless steel were investigated by measuring variable energy Doppler broadening energy spectra (DBES) of positron annihilation and positron annihilation lifetime (PAL). Experimental results showed that hydrogen damage starting from the surface to the bulk has a significant variation with depth. The increase in S-parameter near the surface after hydrogen-charging mainly comes from hydrogen damage; however the increase in S-parameter in the bulk after hydrogen-charging mainly comes from structural defects (e.g. dislocations) induced due to hydrogen-charging. Positron lifetime analysis of two lifetime components is also discussed, and the size of defects induced due to hydrogen-charging is analyzed.