1. An image capturing method executed by an image capturing apparatus including an illumination that illuminates a subject, the image capturing method comprising: continuously generating, using a processor, one or more OFF images in which the subject is captured with the illumination turned OFF, for a first number of times; continuously generating, using the processor, ON images in which the subject is captured with the illumination turned ON, for a second number of times; continuously generating, using the processor, one or more OFF images in which the subject is captured with the illumination turned OFF, for the first number of times; computing, using the processor, a difference image between each of the generated ON images and the OFF image corresponding to the ON image among the generated OFF images; and integrating, using the processor, the computed difference images.