The present invention is characterized by the following points:In a biochip reader used for reading a measurement sample image by light beam irradiation, a correction method for the distribution of quantity of light which is devised to remove the influence of shading for the whole image and such a biochip reader can be realized by correcting non-uniformity in said quantity of light in light beam irradiation by dividing the quantities of light of pixels in a measured image obtained from the measurement of a measurement sample by a distribution of quantity of light in an image obtained from the measurement of a uniform fluorescent plate that presents a uniform fluorescent light distribution, the positions of pixels in the measured image being correspondent to those in the image obtained through the above uniform fluorescent plate measurement.