Abstract: An X-ray inspection apparatus includes an X-ray radiating part, an X-ray detecting part, a mass estimation unit and a mass class determination unit. The X-ray radiating part is configured and arranged to radiate X-rays to an inspection target. The X-ray detecting part is configured and arranged to detect the X-rays radiated from the X-ray radiating part that transmitted through the inspection target. The mass estimation unit is configured to estimate a mass of the inspection target based on an amount of the X-rays detected by the X-ray detecting part. The mass class determination unit is configured to determine which mass class among a plurality of mass classes within a preset range the inspection target belongs to based on the mass of the inspection target estimated by the mass estimation unit.