Inorganic-organic composite materials are commercially utilized over a wide variety of industrial fields. The information on the distribution of inorganic and organic components on a nanometer scale is important for understanding the chemistry of the composite materials. In this study, the distribution of polycarbonate (PC) oligomer within a glass fiber reinforced PC was investigated using time-of-flight secondary ion mass spectrometry (ToF-SIMS) and principal component analysis (PCA). As a result, PCA indicated a component differentiating PC oligomer from PC polymer and revealed the homogeneous distribution of PC oligomer within the glass fiber reinforced PC. Therefore, a combination of ToF-SIMS and PCA is useful for identifying the detailed distribution of PC oligomer and evaluating the property of glass fiber reinforced PC. [DOI: 10.1380/ejssnt.2015.47]