PURPOSE: To obtain a surface-roughness measuring apparatus wherein the roughness of a surface and the displacement of the surface can be measured simultaneously by using one laser light source.

CONSTITUTION: A laser beam is generated by a semiconductor laser 1, the laser beam is condensed by a condensing lens 4 and projected perpendicularly onto the surface of an object 7 under test, reflected light 8 with reference to a projection from the condensing lens 4 is condensed by a condensing lens 10, and an image of the reflected light is formed on a position measuring element 12 for surface displacement detection. In addition, a positive reflection component from the surface of the object 7 under test is taken out by a mirror 3 which has been arranged and installed between the semiconductor laser 1 and the condensing lens 4, and the specular reflection component is photodetected by a phototransistor 14.