According to an embodiment, a radiation measuring apparatus includes a detector, comparators, a threshold controller, counters, and a generator. The detector includes plural detecting elements each configured to convert energy of incident radiation into a first electrical signal. The comparators correspond to the respective detecting elements, each comparator being configured to output a second electrical signal when a level of the corresponding first electrical signal is not less than a threshold. The threshold controller is configured to supply a first value as the threshold to the respective comparators at a first time, and supply a second value as the threshold to the respective comparators at a second time. The counters correspond to the respective comparators, each counter being configured to count the corresponding second electrical signal. The generator is configured to generate a pulse height frequency distribution of the radiation by using counts of the counters.