A three-dimensional measuring device includes a light source unit, a light projecting optical unit, a light receiving optical unit, a light receiving element, a scanning unit, an angle detector, an illumination light source unit, an image pickup unit and a control arithmetic unit. The control arithmetic unit comprises a distance data processing unit for controlling the scanning unit, for calculating a distance to the object to be measured based on a received light signal, and for calculating a three-dimensional data of the object based on a calculated distance and a detection signal from the angle detector, and an image data processing unit for acquiring an illuminated image and an unilluminated image, for acquiring a difference image based on both images, for detecting a retroreflective target based on the difference image and a detected intensity of a reflected light from the difference image, and for calculating a position of the target.