1. An image processing apparatus comprising: an interface configured to receive an input of a plurality of images acquired by imaging a specimen stained with non-fluorescent dye at a plurality of wavelength bands that are different from one another; and a processor comprising hardware, wherein the processor is configured to: calculate a characteristic amount representing auto-fluorescence emitted by the specimen based on the plurality of images; and determine a wavelength band of fluorescence where a fluorescence labeled antibody is superimposable or not superimposable on the specimen stained with the non-fluorescent dye based on the characteristic amount.