The detailed chemical kinetic model based on elementary reactions was developed by adding reactions associated with the formations of benzene oligomers such as quaterphenyl (C24H18) and quinquephenyl (C30H22) and the overall reactions on coke formation to the available model reported previously [Norinaga, K; et al. J. Anal. Appl. Pyro., 2009]. This extended model was critically evaluated by comparisons of the computed results with experimental data on the benzene pyrolysis performed with an atmospheric flow reactor at temperature ranging from 1123 to 1223 K, residence time up to 4 s, and benzene partial pressure of 10.1 kPa [Kousoku, A.; et al. J. Chem. Eng. Jpn.; accepted for publication]. The extended model showed improved capabilities in predicting product distribution in the benzene pyrolysis, including the yields of unreacted benzene as well as primary products such as benzene oligomers, low molecular weight gaseous products such as hydrogen and methane, and soot/coke. In contrast, the original model significantly underpredicted the conversion of benzene and could not predict the formations of benzene oligomers larger than terphenyl and coke. Acceptable agreements in oligomer yields obtained theoretically and experimentally indicate that the higher oligomer formations that had been ignored in the previous research are important reaction pathways leading to polycyclic aromatic hydrocarbons in the primary stage of benzene pyrolysis.