A radiation analyzer includes a transition edge sensor for detecting radiation and a cold head that cools the transition edge sensor. A current detecting mechanism detects a current flowing in the transition edge sensor, and a peak analyzing unit measures a peak value based on the current detected by the current detecting mechanism. A first heater is configured to heat the cold head to keep a temperature of the transition edge sensor constant. A sensitivity correction operating unit is configured to correct a sensitivity of the transition edge sensor based on a relation obtained in advance between an output of the first heater and the peak value measured by the peak analyzing unit.