To inexpensively form an injection-molded article in a favorable looking manner by primary and secondary injection molding accompanied by the movement of a mold, in the manufacturing of the injection-molded article which is formed by making a pair of half-split molded articles abut against each other.

The hollow injection-molded article is manufactured through the following steps: a lens body 2 and a housing body 4 which are half-split are molded in a primary injection step, and abut against each other; and a resin material 5 is secondarily injected into an abutting portion, so that the lens body 2 and the housing body 4 can be integrated to each other. In this case, the injection-molded article is formed in such a manner that a glass transition point of the housing body 4 as one of the half-split molded articles is set to be equal to or higher than that of the lens body 2 as the other half-split molded article.