In the present study, we investigated the effect on growth and photosynthesis of Ulva prolifera using different light emitting diodes (LEDs) and a fluorescent light. The relative growth rates under blue LEDs, red LEDs and a fluorescent light were obtained high values, on the other hand, green LEDs were obtained low value. The gross photosynthetic rate under blue LEDs was showed the highest value within all light sources, whereas that under green LEDs condition was showed low value. Thus, it was clarified that the growth and photosynthesis of U. prolifera were promoted by using blue LEDs and/or red LEDs, and that these were inhibited by using green LEDs. It was thought that their tendencies were caused from relations between the absorption spectrum of U. prolifera and the emission spectrum of each light source. These results suggest that the selective use of LEDs were useful for growth promotes and stock culture and so on.