In the course of research of the relation between color vision and fatigue, use of an electric-motor type color-mixer as a new method of measuring fatigue was considered, and, accordingly, the changing phases in relation to a few experimental load work were duly observed, on a result of which the following conclusion was obtained. (1) Provided that illumination is constant, the flicker frequency will become larger as the difference of luminosity of the test charts mounts. (2) Provided that the difference of luminosity of the test charts is constant, a straightline relation is formed between the flicker frequency and the logarithm of illumination. (3) The new method of measuring fatigue by use of an electric-motor type color-mixer, newly worked out by the present author, has been named the color-mixing flicker test. (4) Working on the same principle as the conventional flicker test, the new method is considered to be superior to the former. (5) This method is considered to be highly sensitive and efficient as a method of measuring fatigue.