The invention discloses a high-precision scanning mine detection device and a scanning detection method, and particularly relates to a device for judging existence of landmines and precisely locatingthe landmines through a PGNAA (Prompt Gamma-Ray Neutron Activation Analysis) technology. The high-precision scanning mine detection device is composed of a neutron source item system, a detection system, a shielding protection system and an energy spectrum analysis system, wherein the neutron source item system is used for exciting nitrogen feature gamma rays in a landmine sample, detectors collect the gamma rays and measure the energy spectrum, the shielding protection system of the detectors is made of a boron-containing polyethylene material, the activation interference of the detectors isreduced, and meanwhile, neutron damage of the detectors is lowered. According to the high-precision scanning mine detection device, the signal-to-noise ratio is regarded as a device design evaluationcriterion, the overall scanning mine detection device is designed based on a novel device evaluation optimization method, the signal-to-noise ratio is high, and the measurement level is improved; meanwhile, a novel scanning method is utilized for mine detection, the measurement time is shortened, and the precision of position detection of the landmines is improved at the same time.