Provided is a compact, low-cost optical measuring apparatus capable of acquiring an image of a target to be measured without moving a mirror or using a wavelength-scanning light source or beam splitter. A laser beam emitted from a light source is split into first and second beams, and the first beam is focused as a signal beam onto the target by a lens for irradiation purposes, while the second beam is reflected as a reference beam by a mirror without irradiating the target. Then, a signal beam reflected by or scattered by the target is multiplexed with the reference beam and then enters interference optics, whereby three or more interference beams with different phases are generated and detected by photodetectors. Then, the detection signals are operated by a signal processing unit. During the measurement, the focus position of the first beam is moved at least in the optical axis direction.