Two-dimensional grazing incidence X-ray diffraction (2D-GIXD) is one of the powerful methods to analyze crystal growth and structure of organic thin films. In this report, we show some experimental examples of 2D-GIXD measurements on organic semiconductor thin-films performed at SPring-8. First, polymorphic transformation of pentacene depending on film thickness observed by means of in-situ real-time 2D-GIXD is shown. Secondly, real-time observation of change in structure during thin-film growth of oligothiophenes by means of 2D-GIXD is shown. Finally, a result of crystal structure analysis from 2D-GIXD data of polycrystalline an oligothiophene thin film is reported.