There is provided an apparatus and method for three-dimensional measurements by shining an object to be measured with plural laser beams while scanning. Even if the optical intensity of laser beams is weak, light disturbance is accurately separated to perform real-time three-dimensional measurement. A laser beam emitted from a laser source is separated into the plural beams of slit light with a predetermined angle at a hologram plate. These two beams are used for scanning and irradiating the object by a scanning mirror. These beams are reflected and read to determine whether or not an interval between these beams corresponds to the predetermined angle.