An optical displacement measuring apparatus utilizing triangulation, includes a laser for projecting a laser light beam with a first optical axis onto a surface of an object whose displacement is to be measured; an array of photodetectors for receiving light reflected from the object and for generating a positional signal as an image displacement .delta.; a condensing lens for receiving the light reflected from the object and for supplying the reflected light to the detector array along a second optical axis intersecting the first optical axis at angle .theta., the detector array being inclined at an angle .phi. with respect to the second optical axis; a determining device for non-linearly determining surface displacement as a function of the image displacement .delta. and the angles .phi. and .theta., with the relationship between the image displacement .delta., the surface displacement and the angles .phi.and .theta. always being identical, regardless of the angle .phi..