According to an embodiment, a neutron measurement apparatus has: a neutron detector; a gamma ray detector; a neutron detector signal processing unit which performs Fourier transform on the signals received for a prescribed period, generates neutron detector signal frequency data in a frequency domain, calculates the neutron-detection signal power spectrum and stores it; a gamma-ray detector signal processing unit which performs Fourier transform on the signals received for a prescribed period, generates gamma ray detector signal frequency data in a frequency domain, calculates gamma ray detector signal power spectrum and stores it; and a neutron calculation unit which generates a neutron signal by removing a part contributed by the gamma ray detector signal power spectrum from the neutron detector signal power spectrum.