A light-irradiating device according to the disclosure includes: a light-emitting element; a housing in which the light-emitting element is disposed, the housing including a light-irradiating surface provided with an irradiating opening which is capable of allowing light from the light-emitting element to pass therethrough; a flow path configured to supply gas, the flow path including an end located near the irradiating opening of the light-irradiating surface of the housing; and a discharging port configured to discharge the gas, the discharging port being disposed at the end of the flow path, the discharging port including a plurality of first openings arranged in a width direction of the irradiating opening in correspondence with the irradiating opening, and a second opening positioned in correspondence with each end in the width direction of the irradiating opening. This makes it possible to reduce uneven distribution of discharged gas improve the reliability of a curing reaction.