We have investigated correlation between grain boundary character and susceptibility to sensitization using SUS304 stainless steel foil with coarse-grained structure. The steel foil of 100 µm thickness was heated at 1473 K for several periods, and a heating time of 604.8 ks was selected to prepare the specimen with coarse-grained structure, in which a median of grain size was 229 µm. In the specimen, most of grain boundary planes were parallel to the thickness direction. The specimen was sensitized and subjected to the grain boundary corrosion test in oxalic acid solution. Thereafter, the orientation of each grain and the Σ value of each grain boundary were determined by the electron backscattering diffraction (EBSD) method. The corrosion width at the grain boundary positively corresponding to a degree of sensitization increased with an increase in Σ value, and became stable as the value was more than 19. In addition, the corrosion width at Σ3 grain boundary was scattered. Since most of the grain boundary planes were parallel to the thickness direction of the specimen, orientation to each plane of Σ3 grain boundary was determined from the EBSD results, and the degree of coincidence for atom sites on the Σ3 plane was analyzed. As a result, orientations of the observed Σ3 planes were parallel to the common rotation axes characterizing Σ3 coincidence site lattice (CSL) in space, and the Σ3 grain boundary had three types of planes with different CSL. An area of the unit cell for CSL of the grain boundary plane identified as Σ3 was selected as an index of grain boundary character, and an increase in the area correlated to an increase in the corrosion width.