An image forming apparatus includes lasers to respectively emit lights having central wavelengths different from each other, an imager to output an image signal upon receiving light from a subject, a laser wavelength-specific image information acquirer to acquire, from the image signal output from the imager, pieces of laser wavelength-specific image information, and an image former to combine the pieces of laser wavelength-specific image information supplied from the laser wavelength-specific image information acquirer, so as to form an observation image in each mode included in the observation modes.