A device of an embodiment includes: an optical mechanism; a control computation unit that controls driving of the optical mechanism, acquires a tomographic image of skin by processing an optical interference signal from an optical system, and calculates a network of blood vessels on the basis of the tomographic image; and a display device that displays an image of the network of blood vessels. The control computation unit sets a reference profile obtained by function approximation of an intensity profile in a depth direction of the acquired tomographic image, calculates a difference between an intensity value on the reference profile and an actual intensity value as an outlier V, the intensity values being those in the depth direction in the tomographic image, determines, as blood vessels or blood vessel candidates, coordinates with the outliers V within a predetermined blood vessel determination range, and calculates the network of blood vessels.