In a memory unit 6, there is stored a correction table for each candidate value of an output set value of each of LED units 2. If UV rays have ever been emitted so far by the LED units 2, each of which is formed of a plurality of LED chips 8, then a PLC 5 acquires, upon setting of a output set value by an operation unit 53, a correction value corresponding to a cumulative emission time up to a previous emission, from the correction table of the output set value. Thereafter, the PLC 5 sets the magnitude of the power supplied to each of the LED units 2 using the acquired correction value. If an output set value different from a previous output set value is set, the PLC 5 obtains the correction value starting from the cumulative emission time upon modification. As a result, the UV irradiation apparatus enables power consumption necessary for emission of UV rays to be reduced, and UV ray output to be kept constant regardless of the cumulative emission time, even if the output set value is modified.