A measurement of standard light is performed during radiation measurement for gain correction and offset correction of radiation measurement apparatus. The standard light emitted by a LED falls on a PMT. An output signal of a preamplifier corresponding to the PMT is entered into a system controller after being subjected to predetermined analog signal processing. The system controller calculates a gain correction value and an offset correction value on the basis of initial correction values and an output value of the preamplifier, whereby gain control and offset control can be performed stably even in radiation measurement.