A total reflection terahertz wave measuring apparatus comprising: a light source for outputting light; a branching part for branching the light output from the light source into two, to output one of the lights branched into two as a pump light and the other one as a probe light; a terahertz wave generating element for generating and outputting a terahertz wave by receiving the pump light output from the branching part; an internal total reflection prism adapted to receive the terahertz wave output from the terahertz wave generating element on an entrance plane, to make the received terahertz wave be propagated internally to be totally reflected by a reflection plane, and to output the terahertz wave from an exit plane to the outside; and a terahertz wave detecting element for receiving the terahertz wave output from the exit plane of the internal total reflection prism and the probe light output from the branching part, to detect a correlation between the terahertz wave and the probe light, wherein the terahertz wave generating element is provided to be integrated with the entrance plane of the internal total reflection prism, wherein the terahertz wave detecting element is provided to be integrated with the exit plane of the internal total reflection prism, wherein the internal total reflection prism has, in addition to the entrance plane, the reflection plane, and the exit plane, a first secondary reflection plane for reflecting the terahertz wave received by the entrance plane to be propagated internally toward the reflection plane, and a second secondary reflection plane for reflecting the terahertz wave reflected by the reflection plane to be propagated internally toward the exit plane; wherein the first secondary reflection plane has the shape of an off-axis paraboloidal mirror to yield a collimation effect on the terahertz wave received by the entrance plane to be propagated inside the internal total reflection prism and to be incident collimated on the reflection plane; and further wherein information on a subject disposed on the reflection plane of the internal total reflection prism is acquired with an evanescent component of the terahertz wave generated at the time of total reflection of the terahertz wave. a light source for outputting light; a branching part for branching the light output from the light source into two, to output one of the lights branched into two as a pump light and the other one as a probe light; a terahertz wave generating element for generating and outputting a terahertz wave by receiving the pump light output from the branching part; an internal total reflection prism adapted to receive the terahertz wave output from the terahertz wave generating element on an entrance plane, to make the received terahertz wave be propagated internally to be totally reflected by a reflection plane, and to output the terahertz wave from an exit plane to the outside; and a terahertz wave detecting element for receiving the terahertz wave output from the exit plane of the internal total reflection prism and the probe light output from the branching part, to detect a correlation between the terahertz wave and the probe light, wherein the terahertz wave generating element is provided to be integrated with the entrance plane of the internal total reflection prism, wherein the terahertz wave detecting element is provided to be integrated with the exit plane of the internal total reflection prism, wherein the internal total reflection prism has, in addition to the entrance plane, the reflection plane, and the exit plane, a first secondary reflection plane for reflecting the terahertz wave received by the entrance plane to be propagated internally toward the reflection plane, and a second secondary reflection plane for reflecting the terahertz wave reflected by the reflection plane to be propagated internally toward the exit plane; wherein the first secondary reflection plane has the shape of an off-axis paraboloidal mirror to yield a collimation effect on the terahertz wave received by the entrance plane to be propagated inside the internal total reflection prism and to be incident collimated on the reflection plane; and further wherein information on a subject disposed on the reflection plane of the internal total reflection prism is acquired with an evanescent component of the terahertz wave generated at the time of total reflection of the terahertz wave.