A seatbelt of a vehicle includes a buckle tilt mounting device for a tongue plate coupled with a seatbelt webbing restraining an occupant seated in a vehicle seat. The buckle tilt mounting device includes a buckle assembly having a buckle and a buckle cable, and further includes a pre-tensioner system having a housing, a driving member, and a pre-tensioner cable. When the pre-tensioner system is actuated at a time of a vehicle collision or at a time a vehicle collision is anticipated, the driving member retracts the pre-tensioner cable inside the housing such that the buckle assembly is rotatably moved and configured to reduce submarining load on the occupant.