We have developed a new microscope light collection unit and time-correlated single photon counting system, which can be applied for single molecular spectroscopy under various ambient gas and high vacuum conditions as well as under various electromagnetic conditions using photonic crystal. In this paper, we describe the development of the new apparatus and report some experimental results of single molecular spectroscopy for a colloidal quantum dot and a fluorescent molecule. Finally, we would like to emphasize a wide range of applications of the new apparatus for various spectroscopic measurements.