A medical photometer includes a processor and a memory that stores an instruction readable by a computer. When the instruction is executed by the processor, the medical photometer acquires an intensity of one of a first intensity signal and a second intensity signal, the first intensity signal corresponding to an intensity of a first light beam that has a first wavelength and that is transmitted through or reflected from a tissue of a living body, and a second intensity signal corresponding to an intensity of a second light beam that has a second wavelength and that is transmitted through or reflected from the tissue of the living body acquires an intensity ratio of the first intensity signal and the second intensity signal, and detects an artifact of the living body based on the acquired intensity and the acquired intensity ratio.
