PROBLEM TO BE SOLVED: To provide an artificial light source unit which can irradiate cultivated plants or the like with light having a desired color and can thereby properly adjust the growth state of the plants or the like. SOLUTION: This light-emitting device (artificial light source unit) comprises many light-emitting diodes for emitting light having a desired color, a base on which the many light-emitting diodes are arranged in parallel, and a light- transmitting water-proof cover for covering the many light-emitting diodes on the base. The light-emitting device (artificial light source unit) can freely be set, has a high water-proof property, and hardly generates heat. The color of the emitted light of the light-emitting diodes can be selected for a desired color for promoting the growth of the plants or the like, and further the emitted light of the light-emitting diodes can be adjusted to a desired emitted light quantity, a desired light-emitting timing and a desired light-emitting time.
