A photosensor device, which is constituted of a light-applying fiber 107 to apply an inspection light to a subject to be inspected; a light-receiving fiber 108 to receive a reflected light from the subject to be inspected; a laser beam source 114 to emit the inspection light to the light-applying fiber; and a photosensor 113 to receive the reflected light via the light-receiving fiber; which are disposed in a casing 102. A disk inspection apparatus for inspecting surface conditions of a disk, which is constituted of a turning table 204 for rotating the disk; a photosensor body 205 disposed opposite to the surface of the disk; and a transfer means for reciprocally transferring the photosensor body in a direction perpendicular to a rotating direction of the disk along the surface of the disk; wherein the above photosensor device is utilized as the photosensor body.