To provide a portable neutron dosimetric device having excellent energy characteristic.

A detection part 100 has a constitution wherein a human body side detector 110A and an incidence side detector 110B are buried in a moderator block 120. The detectors 110A, 110B each detects a nuclear reaction product between thermal neutrons and a nuclear reaction substance 112. Detection signals from the respective detectors 110A, 110B are counted respectively by counters 130A, 130B. Information showing a relation between energy of incident neutrons and the ratio of a counting rate between the two detectors 110A, 110B is registered in an energy characteristic table 150. An operation part 140 estimates the energy of the incident neutrons on reference to the energy characteristic table 150 from the ratio of the counting rate between the counters 130A, 130B, determines a dose conversion coefficient corresponding to the energy from a doze conversion table 160, and calculates the neutron doze by using the coefficient and the counting rate of the counter 130A.