Surface-treatment effects on IGSCC susceptibility of sensitized 304 stainless steel in 561 K pure water were investigated concerning machining, grinding and shot peening. Main results obtained are as follows:(1) In a subsurface layer severly worked by machining or grinding, residual tensile stress of 300–400 MPa and strain-induced martensite of 4–6% in the volume fraction were observed. The work hardening zone produced by these treatments was about 50 μm in thickness.(2) Large compression of 500–750 MPa was retained after the shot peening in the subsurface. A large work-hardened zone 250∼350 μm thick and martensite of approximately 20% in the volume fraction were induced by this surface-treatment. In the case of high injection energy peened by 1.0 mm diameter shot, very large surface roughness of about 70 μm and microcracks were observed on the as-worked surface.(3) The susceptibility of IGSCC of sensitized 304 stainless steel in 561 K pure water was increased by machining and grinding when tension above 300 MPa was produced on the worked surface.(4) When the surface roughness was below about 20 μm and residual compression was above approximately 500 MPa, the shot peening treatment suppressed initiation of IGSCC in the SCC test up to the applied stress of 2.00 σy. However, even if residual compression was larger, occurrence of IGSCC was accelerated by the shot peening under the conditions of higher applied stress and more rough surface than the above values.