Optical detection method and optical detection apparatus, as well as to provide an endoscope and a microscope can be heterodyne detected with high SN ratio and high sensitivity detected light desired. If the local light generating means 10 for generating local light having a light plurality of frequency components in the optical frequency band of light to be detected within a fixed period of time, and the detected light and the local light generated by the local light generator 10 has an optical multiplexing means 20 for the waves, and a photoelectric converting means 30 for generating a beat signal of the detected light and local light and photoelectrically converts the light output from the optical multiplexing means 20, the output of the photoelectric converting means 30 and heterodyne detection of the detected light based on.所望の被検出光を高感度かつ高SN比でヘテロダイン検出できる光検出装置および光検出方法、並びに、顕微鏡および内視鏡を提供する。一定時間内に被検出光の光周波数帯域内に複数の光周波数成分を有する局発光を発生する局発光発生手段10と、局発光発生手段10から発生される局発光と被検出光とを合波する光合波手段20と、光合波手段20から出力される光を光電変換して局発光と被検出光とのビート信号を生成する光電変換手段30とを有し、光電変換手段30の出力に基づいて被検出光をヘテロダイン検出する。
