It is an object of the present invention to provide a cleaning method of and a cleaning apparatus for removing organic matters such as phthalates that have deposited on the surface of a semiconductor substrate while restraining the growth of a natural oxide film. The present invention provides a method of cleaning a semiconductor substrate, which comprises irradiating a semiconductor substrate contaminated by organic matters such as phthalic acid, phthalate and derivatives thereof with vacuum ultraviolet light having a wavelength within a range from 165 to 179 nm in an atmosphere of oxygen or air that is introduced from an O2 or air intake port, thereby decomposing and removing the contaminant.