A medical photometer comprising: a processor; and a memory that stores an instruction readable by a computer, wherein, 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, cancels out a variation of the detected intensity due to pulsation and detects an artifact of the living body based on a temporal variation of the acquired intensity ratio, wherein a ratio of a first extinction of a first light absorber at the first wavelength and a second extinction of the first light absorber at the second wavelength is different from 1, a third extinction of a second light absorber at the first wavelength is higher than the first extinction, a fourth extinction of the second light absorber at the second wavelength is higher than the second extinction, and a ratio of the third extinction and the fourth extinction is approximable by 1, the medical photometer further comprises: a first light emitter that emits the first light beam having the first wavelength; a second light emitter that emits the second light beam having the second wavelength; and a detector that outputs the first intensity signal and the second intensity signal. a processor; and a memory that stores an instruction readable by a computer, wherein, 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, cancels out a variation of the detected intensity due to pulsation and detects an artifact of the living body based on a temporal variation of the acquired intensity ratio, a ratio of a first extinction of a first light absorber at the first wavelength and a second extinction of the first light absorber at the second wavelength is different from 1, a third extinction of a second light absorber at the first wavelength is higher than the first extinction, a fourth extinction of the second light absorber at the second wavelength is higher than the second extinction, and a ratio of the third extinction and the fourth extinction is approximable by 1, the medical photometer further comprises: a first light emitter that emits the first light beam having the first wavelength; a second light emitter that emits the second light beam having the second wavelength; and a detector that outputs the first intensity signal and the second intensity signal. a first light emitter that emits the first light beam having the first wavelength; a second light emitter that emits the second light beam having the second wavelength; and a detector that outputs the first intensity signal and the second intensity signal.