Our group is currently developing a multilayer neutron spectrometer based on moderator combination selection to evaluate neutron energy spectra in irradiation fields for boron neutron capture therapy (BNCT). In a previous study, we optimally selected (based on simulations) liquid moderator combinations of the spectrometer to achieve high accuracy in the evaluated neutron energy spectra. According to the optimization result, we conducted a spectrometer verification test in the BNCT irradiation field at the Heavy Water Neutron Irradiation Facility of Kyoto University Reactor (KUR-HWNIF). The neutron energy spectrum result was evaluated, and the uncertainty was found to be less than 15%. The experimental results prove that the multilayer neutron spectrometer based on moderator combination selection effectively evaluates the neutron energy spectrum in a BNCT irradiation field.