Massive neutrino detector experiments, which are oriented for the electron antineutrino observation, calibrate their neutron tagging efficiency using AmBe neutron sources. Super-Kamiokande, a large water Cherenkov detector experiment, also started their new experimental phase SK-Gd for the astrophysical antineutrino observation. In their calibration, AmBe neutron source applied used with surrounding BGO scintillator crystals. The neutron emission is triggered and identified by scintillation light emission of 4438 keV gamma-ray from the source, and thus the neutron tagging efficiency is evaluated. Super-Kamiokande reports a relative 10% inconsistency between the efficiency value of the simulation and measurements. The reason should be investigated rapidly, and a sideband study was started to measure neutron and gamma rays from the AmBe source. In the presentation, the progress of measurements will be reported as follows: energy spectrum measurements for neutron with gamma-ray emission based on time-of-flight, emission ratio of the neutron with/without gamma-ray.