An in-house grazing incidence X-ray scattering (GIXS) apparatus has been newly developed for characterizing the surface structure at a microscopic level. This system consists of an 18-kW relating anode X-ray generator, a flat or channel-cut Ge(111) single crystal monochromator and crossed double-axis diffractometers. Using this new apparatus, the X-ray reflection profiles of chromium oxide films grown on colored stainless steels were measured. The values of critical angle and thickness of films are estimated and the density variation of chromium oxide films is suggested. Surface diffraction profiles from the SUS304 stainless steel oxidized for 240 s at 1073 K in air were also measured in the vicinity of the critical angle with the GIXS geometry. The observed peaks were identified as Cr2O3, FeCr2O4 and the austenite phase of SUS304. The depth profile has also been discussed from the integrated intensities of both phases of oxide and the stainless steel.