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 a first light attenuation of a first light beam that is transmitted through or reflected from a tissue of a living body, and that has a first wavelength, based on a first intensity signal corresponding to an intensity of the first light beam, acquires a second light attenuation of a second light beam that is transmitted through or reflected from the tissue, and that has a second wavelength, based on a second intensity signal corresponding to an intensity of the second light beam, calculates a tissue thickness based on a ratio of the first light attenuation and the second light attenuation, and detects an artifact of the living body based on a temporal variation of the tissue thickness.
