Noncontact film thickness measurement device includes an ultra short light pulse light source generating a repetitive ultra short light pulse laser, of which wavelength is in an area from visible region to near-infrared region, a light dividing device for dividing the ultra short light pulse laser into a pump light and a probe light, a light retarding device for controlling to retard the time of either one of the pump light and the probe light, a terahertz wave pulse generating device for generating a terahertz wave pulse by inputting the pump light and generating the terahertz wave pulse in a coaxial direction relative to a remaining pump light outputted without being used for generation of the terahertz wave pulse in the pump light, a light incident optical system for inputting the terahertz wave pulse to an object of which film thickness is to be measured, a light receiving optical system for receiving a terahertz echo pulse reflected from the object by inputting the terahertz wave pulse and a detecting device for detecting an electric field amplitude time resolved wave form of a terahertz echo pulse with the probe light.