To provide a surface lighting system of which the manufacture cost and running cost during measurement are low, the system body is hardly affected by heat generation, and the operation is easy.

This surface lighting system includes a case section having a halogen light source installed at the focal position of a parabolic mirror, a collimator lens for deflecting light emitted from the light source in parallel to the optical axis, a slit for varying the width and thickness of the light flux having transmitted through the collimator lens, and a first right-angled isosceles triangle prism for total-reflecting the light having come through the slit upwardly with respect to the axial direction by the slope of 45, and a second prism for total-reflecting the light having transmitted through the first prism of the case section on the slopes of 45 whose reflecting surfaces are in parallel.