A method and apparatus for rapidly and accurately determining fiber orientation of paper which is at a standstill or moving in a paper machine employs a projector which projects a light beam perpendicularly to an incident surface of the paper to be tested. The light beam reflected by the incident paper surface is caught by eight or more light receivers distributed on a circumference of a circle on the incident surface side of the paper. The circle is defined in a plane extending in parallel to the paper surface and having an axis at the point where the above-mentioned parallel plane intersects an axis of the incident light beam. A light information signal output from the light receivers are subjected to a processing to obtain the fiber orientation characteristics, such as fiber orientation index value and fiber orientation angle.