Fine particles were collected at a suburban site in the inland Kanto plain, Japan, in the spring and winter of 2007, and the summer of 2008. Organic carbon (OC), water-soluble organic carbon (WSOC), elemental carbon (EC), inorganic ions, and water-soluble organic compounds (dicarboxylic acids and levoglucosan) were analyzed. The WSOC/OC ratio was the highest in summer, followed by in spring, suggesting that organic aerosols were influenced by aging. The concentrations of total diacids (C2–C9) in spring and summer were higher than in winter. In each season, WSOC showed a strong positive correlation with the total diacids. Levoglucosan, which is recognized as a biomass burning tracer, was observed in a considerably higher concentration in winter than in spring or summer. In winter, WSOC also showed a strong positive correlation with levoglucosan. These results indicate that secondary formation is important as a source of WSOC and OC especially in the warm seasons, although emissions from biomass burning also contribute to WSOC in winter. By using the combination of source profile for biomass burning emission and EC tracer method, OC derived from biomass combustion in winter was calculated to be 47% of OC and OC derived from secondary formation in summer was calculated to be 75% of OC.