It is important to measure the toner mass distribution on paper, on intermediate transfer belts and on OPCs (organic photoconductors) to analyze the structure of the toner image in electrophotography. However, toner distributions are difficult to measure. When the amount of the black toner is high, the reflectance is very low. Therefore, a charge-coupled array (CCD) camera cannot detect minor differences in the reflectance. Additionally, when the exposure time is long, the signals from the paper are saturated. The purpose of this paper is to establish a toner mass distribution measurement method. To archive this, we propose a measurement method using a multiple exposure. First, the toner area and the paper are measured by the multiple exposure process. Next, based on the relationship between the exposure time and the brightness values of the CCD camera, two approximately linear equations are obtained by the least squares method and the two lines slopes are obtained from these equations. The toner reflectance is calculated using the line slopes. If we calculate the reflectance at each pixel of the camera, then the reflectance distribution can be obtained. This method can prevent detection shortages and saturation of the camera to enable measure toner and paper measurements while using entire the dynamic range. Furthermore, the method can reduce random noise to calculate the reflectance using multiple images of the same area. Finally, we propose an unfixed toner mass prediction model. This model can vary the reflectance relative to the toner mass, and the toner mass distribution can thus be obtained. This method can visualize the uniformity of the toner mass, and we expect this method to be used for image analysis.