A device of an embodiment includes: an optical mechanism that guides light from a light source to skin tissue to scan the skin tissue; a control computation unit that controls driving of the optical mechanism, acquires tomographic images of the skin by processing optical interference signals from the optical system, and calculates a network of blood vessels on the basis of the tomographic images; and a display device that displays the network of blood vessels. The control computation unit computes autocorrelation values at coordinates in epidermis corresponding regions of the tomographic images, excludes combinations of tomographic images with the computed autocorrelation values corresponding to predetermined low autocorrelation, computes autocorrelation values at coordinates in dermis corresponding regions, determines coordinates at which the autocorrelation values in the dermis corresponding regions are within a predetermined low correlation range to be blood vessels or blood vessel candidates, and calculates a network of blood vessels.