Abstract: A method and an instrument are, herein, disclosed for measuring the absorbed dose rate of beta-ray in sites of the human body. The instrument of this invention consists of a thin scintillator, a linear amplifier, a pulse selector having disposed in parallel therein a plurality of pulse height selection mechanisms for selectively setting the lower and upper limits of pulse height discrimination according to an epidermal thickness of human tissue, and a dose rate indicator. The method and the apparatus of this invention are characterized by making the relationship between the counting rate per fluence rate and the maximum energy of beta-ray equal to the relationship between the absorbed dose rate per fluence rate and the maximum energy of beta-ray, and therefore, the absorbed dose rate can be measured independent of the energy of beta-ray.