The operation unit of radiation monitoring equipment reads in a real countable number (this time) and a cumulated countable number (previous time) in a every operational cycle, and judges whether the real countable number (this time) is within a permissible range, if the real countable number (this time) is judged to be within the permissible range, it is judged whether a number of times deviated from the permissible range is equal to zero or not, if the number of times deviated from the permissible range is judged to be equal to zero, a regular processing is performed, if the real countable number (this time) is judged to be out of a permissible range, 1 is added to the number of times deviated from the permissible range and further it is judged whether the added number of times deviated from the permissible range is equal to 1 or not.