The UV light irradiation device includes a chamber having a space for accommodating therein an irradiation target, and a plurality of light-emitting diodes provided at an inner surface of the chamber. A controller is configured to control lighting of the plurality of light-emitting diodes. The light-emitting diodes include a plurality of first light-emitting diodes, each having a peak wavelength in a range of 280 nm to 310 nm, and a plurality of second light-emitting diodes, each having a peak wavelength in a range of 310 nm to 405 nm. The controller includes a lighting control section that is configured to light up the first light-emitting diode before lighting up the second light-emitting diode.
