Abstract. In this study, conspicuity and readability of the text on light-emitting diode (LED) information boards were evaluated by psychological experiments, and the influences of color combinations of text / background, luminance, and shadow were evaluated quantitatively. In recent years, LED boards have been able to display full-color images, and they have many functions to highlight text. Therefore, it is assumed that the LED board ability to function may be reduced depending on the way it is used. We investigated the relationship of color combinations of text and background, luminance, and shadow to conspicuity and readability to evaluate ease and efficiency of information communication via the LED board. We found that (1) the size of the area with high luminance affected conspicuity, (2) the difference of luminance of the part adjacent to the text/background affected readability, and (3) shadow affected both conspicuity and readability. Furthermore, trade-off between them was confirmed.