An image processing method includes: acquiring correction data for correcting first image data into second image data, the first image data being generated by an imaging device when a subject is irradiated with three rays of narrow band light having wavelength bands narrower than those of spectral sensitivity of pixels R, G, and B, and having spectrum peaks within wavelength bands of the spectral sensitivity of the pixels R, G, and B, and the second image data being deemed to be generated by the imaging device when white light is emitted； acquiring the first image data when the subject is irradiated with the three rays of narrow band light； generating color image data of the second image data using the first image data and the correction data； and calculating oxygen saturation of the subject using a pixel value R and a pixel value G included in the first image data.
