In this paper, a method to calculate the value of visual information on image is proposed. The step number of perceptible brightness levels and the division number of minimum perceptible areas at photopic vision are obtained from the visual properties. These values correspond to the length and the kind of the sign in the information theory. First, the capacity of visual information on image is calculated. Then, the amount of visual information on image is calculated. We applied the method to actual image and calculated the value of visual information that observer receives from visual object. Consequently, the capacity of visual information on image can be obtained quantitatively using the proposed method.