In the measuring device and measuring method, confocal measuring principle is utilized. A certain component of an optical measurement signal is, from the point of view of both illumination and imaging, in focus only at one point on the virtual measuring surface. In the measuring device, the surface to be measured always hits a common focus point of the illumination and imaging, whereby a reflection is generated. The reflected optical signal is directed to a detector belonging to the imaging unit, where one picture element of the detector corresponds to a certain focus point, respectively. The optical efficiency received by each picture element is indicated. The light reflecting from the intersection of the virtual measuring surface and the surface of the object produces an intensity maximum for the detector. This maximum point is indicated and converted in the imaging unit (13) into the height of the surface of the object.