BUCKLE DEVICE, SEAT MOUNTING STRUCTURE FOR BUCKLE DEVICE, AND VEHICLE SEAT BELT DEVICE

A buckle device includes: a buckle body to which a tongue portion mounted on a three-point seat belt is to be connected; a connecting member that is flexible and that has a first longitudinal end portion connected to the buckle body; and a force limiter mechanism including a take-up shaft around which a second longitudinal end portion of the connecting member is wound, the take-up shaft being supported below the buckle body in a vertical direction of a vehicle so as to be rotatable relative to a vehicle seat or a vehicle body, and an energy absorbing member that is deformed by rotation of the take-up shaft.