An illuminating apparatus (1) includes a UV light source (21) capable of emitting UV-C with a wavelength component under substantially 250 nm cut off therefrom and UV-B； a visible light source (23) capable of emitting visible light； and a controller (4) for controlling the operations of the UV light source (21) and the visible light source (23). Under the control of the light source (21), (23) by the controller (4), light illumination according to an illumination pattern, which is a combination of first illumination with overlapped UV-C and UV-B and visible light and second illumination with visible light only, is repetitively conducted twice a day. In this way, the production of fungi spores and the growth of hypha resulting in the disease can be well suppressed due to the illumination with UV-C and UV-B on the plant (P1). In addition, since UV-C and UV-B is intermittently used for illumination, the adaption of the plant (1) to UV light can be avoided while facilitating the production of anti-fungi or resistant substances. Thus the disease-resistance can also be well induced and leaf scorch can be prevented. Furthermore, since visible light is continuously used for illumination, it is advantageous in the growth of the plant (P1).植物病害防除用照明裝置(1)包括一可放出除掉約250nm以下波長成分的UV-C以及UV-B的紫外光源(21)、可放出可見光的可見光源(23)、以及控制紫外光源(21)與可見光源(23)動作的控制器(4)。控制器(4)控制各光源(21)、(23)，將上述UV-C以及UV-B與可見光重疊而成的第一光照射，以及僅有可見光的第二光照射所組合成的照射模式反覆進行一日兩回以上的光照射。如此一來，由於可將UV-C以及UV-B照射在植物(P1)上，可確實抑制上述絲狀菌的孢子形成以及菌絲的成長。此外，由於UV-C以及UV-B係間歇性照射，可預防植物(P1)習慣紫外線，可促進抗菌性或抗性物質的產生，確實誘發對病害的抗性，同時防止葉灼。另外，由於連續照射可見光，可促進植物(P1)的生長。
