The purpose of the present disclosure is to provide a computer system, a plant diagnosis method, and a program in which the accuracy of plant diagnosis can be improved. The computer system acquires a visible light image of a plant imaged by a camera, compares the acquired visible light image with a normal visible light image of the plant and performs image analysis, identifies a species of the plant according to the result of the image analysis, identifies an abnormal portion of the plant according to the result of the image analysis, acquires environmental data of the plant, and diagnoses a condition of the plant according to the identified species, the identified abnormal portion and the acquired environmental data.