A photoirradiation device includes an insertion path for inserting a wire rod; a first reflector having a circular arc shape centered on a point shifted from a center of the insertion path by a first distance, one side of the first reflector facing the insertion path being a reflective surface; a second reflector disposed adjacent open edges of the first reflector and having a circular arc shape centered on a point shifted from the center of the insertion path by a second distance that is different from the first distance, one side of the second reflector facing the insertion path being a reflective surface; and a light source that is positioned on an opposite side of the insertion path from the first reflector and that projects light toward the wire rod.