A light-irradiating device of the disclosure comprises: a light-irradiating unit comprising a housing in which a light-emitting element is disposed, the housing comprising a light irradiation surface through which light from the light-emitting element can be transmitted; and a gas supply unit comprising a flow channel connected to a part of the light irradiation surface of the housing. A printing device of the disclosure comprises: the light-irradiating device mentioned above; a conveying unit which conveys a medium to be printed while causing the medium to face the light irradiation surface of the light-irradiating device; and a printing unit which is disposed adjacent to and upstream from the light-irradiating device in a conveyance direction of the medium to be printed.