A light guide member , comprising: first and second ends , the first end being one end, in a length direction (dl), of the light guide member elongated in one direction, the second end being an opposite end of the light guide member from the first end , a light entrance surface (4A or 4B) being provided on at least one of the first and second ends ; a reflective surface that is provided along the length direction (d1) of the light guide member and configured to reflect light from the light entrance surface (4A or 4B); a light exit surface that is provided along the length direction (d1) of the light guide member and allows the light reflected in the reflective surface to exit from, wherein the reflective surface comprises at least one diffusion groove array including diffusion grooves that are arranged in the reflective surface in the length direction (d1) of the light guide member and configured to diffuse the light from the light entrance surface (4A or 4B), each of the diffusion grooves being a groove that is elongated in a direction intersecting with the length direction (d1) of the light guide member , the diffusion groove array comprising, as the diffusion grooves , at least two inspection grooves and a non-inspection diffusion groove , the two inspection grooves being spaced in the length direction (d1) of the light guide member , the non-inspection diffusion groove being between the two inspection grooves the inspection groove differing from the non-inspection groove in that an intermediate part of each of the two inspection grooves in a length direction of each of the two inspection grooves being divided by an ungrooved portion with no groove. first and second ends , the first end being one end, in a length direction (dl), of the light guide member elongated in one direction, the second end being an opposite end of the light guide member from the first end , a light entrance surface (4A or 4B) being provided on at least one of the first and second ends ; a reflective surface that is provided along the length direction (d1) of the light guide member and configured to reflect light from the light entrance surface (4A or 4B); a light exit surface that is provided along the length direction (d1) of the light guide member and allows the light reflected in the reflective surface to exit from, wherein the reflective surface comprises at least one diffusion groove array including diffusion grooves that are arranged in the reflective surface in the length direction (d1) of the light guide member and configured to diffuse the light from the light entrance surface (4A or 4B), each of the diffusion grooves being a groove that is elongated in a direction intersecting with the length direction (d1) of the light guide member , the diffusion groove array comprising, as the diffusion grooves , at least two inspection grooves and a non-inspection diffusion groove , the two inspection grooves being spaced in the length direction (d1) of the light guide member , the non-inspection diffusion groove being between the two inspection grooves the inspection groove differing from the non-inspection groove in that an intermediate part of each of the two inspection grooves in a length direction of each of the two inspection grooves being divided by an ungrooved portion with no groove. <EOS>