Integrated quantum optical circuit is now drawing attention as a way to realize large-scale photonic quantum informationsystems. A missing function for realizing a photonic quantum processor on chip is a “single photon buffer”, where a photon is stored while its quantum state is preserved. Here we report an on-chip single photon buffer based on coupled resonator optical waveguide (CROW). By using a CROW consisting of 400 high-Q photonic crystal line defect nanocavities, a pulsed photon from a correlated photon pair source was successfully buffered for 150 ps, while preserving non-classical intensity correlation.