There is provided a neutron capture therapy apparatus (1) capable of measuring the neutron dose in real time while suppressing a reduction in the measurement accuracy of a neutron beam (N). A real-time dose output unit (40) including a scintillation detector (41), which detects the neutron beam (N) and outputs a signal in real time, and a neutron dose output unit (44), which converts the signal, output from the scintillation detector (41) into a neutron dose using a correction coefficient (45) and outputs the neutron dose in real time, and a correction coefficient setting unit (60) that sets the correction coefficient 45 are provided. The correction coefficient setting unit (60) includes a gamma ray detection section (62) that detects a gamma ray emitted from a gold wire (61) activated by irradiation of the neutron beam (N), and modifies the correction coefficient (45) based on a signal, which is output from the scintillation detector (41) by irradiation of the neutron beam (N), and a dose of the neutron beam (N), which is acquired based on the gamma ray detected by the gamma ray detection section (62).
