RADIATION MONITOR

A radiation monitor includes a high-energy count-rate-measurement functional unit (22a, 22b), a low-energy count-rate-measurement functional unit (23), and an alert-diagnosis functional unit (24). The alert-diagnosis functional unit (24) receives an alert from the high-energy count-rate-measurement functional unit (22a, 22b), receives a low-energy count rate from the low-energy count-rate-measurement functional unit (23), determines whether or not the low-energy count rate is in a set acceptable range by performing synchronizing with alert transmission, determines that the alert is caused by fluctuation, when the low-energy count rate is in the acceptable range, determines that the alert is caused by any of an increase in the ³ ray which is a measurement target or enter of noise, when the low-energy count rate is increased beyond the acceptable range, and outputs results of determination.