A lens array unit includes a first lens array plate, a second lens array plate, and a holder. The holder includes a first surface part provided with a plurality of first through holes respectively corresponding to a plurality of first outer lenses, a second surface part provided with a plurality of second through holes respectively corresponding to a plurality of second outer lenses, and a support part operative to support the first surface part and the second surface part so as to be located at a predetermined distance from each other. The first surface part, the second surface part, and the support part are integrally formed by a light shielding material, and the first lens array plate and the second lens array plate are held by the holder by being inserted into the gap between the first surface part and the third surface part and the gap between the second surface part and the third surface part, respectively.