A vehicle seat belt device (12; 71) comprising: a pair of arm rests (22; 50; 60) that are configured to be disposed on both seat width direction sides of a seat back configuring a vehicle seat and that are rotatable between a storage position, in which the arm rests (22; 50; 60) are placed along a seat up and down direction, and a use position, in which the arm rests (22; 50; 60) are tilted in a seat forward direction from the storage position and placed along a seat front and rear direction; slide members (24; 52) that are respectively disposed at the pair of arm rests (22; 50; 60) and that are slidable along the arm rests (22; 50; 60), distal end portions of the slide members having belt guides through which webbing is passed; a belt anchor that is configured to be disposed on one seat width direction side of a lower portion of the seat back, and to which one end portion of the webbing is anchored; a retractor that is configured to be disposed on the other seat width direction side of a lower portion of the seat back and takes up the other end portion of the webbing passed through the belt guides on the both seat width direction sides, or a retractor that is disposed on the one seat width direction end side of an upper end portion of the seat back and takes up the other end portion of the webbing looped back in another belt anchor which is disposed on the other seat width direction side of the lower portion of the seat back and in which is looped back the webbing extending from the first belt anchor and passed through the belt guides on the both seat width direction sides; and a control unit that, in a state before an occupant is seated in the vehicle seat, causes the pair of arm rests (22; 50; 60) to be held in the storage position and causes the slide members (24; 52) to be held in a state in which the slide members (24; 52) have been slid further in a seat upward direction than a head rest, and that, in a state in which the occupant is seated, causes the pair of arm rests (22; 50; 60) to rotate from the storage position to the use position, causes the slide members (24; 52) to slide toward base sides of the arm rests (22; 50; 60), and causes a predetermined amount of the webbing to be taken up by the retractor. a pair of arm rests (22; 50; 60) that are configured to be disposed on both seat width direction sides of a seat back configuring a vehicle seat and that are rotatable between a storage position, in which the arm rests (22; 50; 60) are placed along a seat up and down direction, and a use position, in which the arm rests (22; 50; 60) are tilted in a seat forward direction from the storage position and placed along a seat front and rear direction; slide members (24; 52) that are respectively disposed at the pair of arm rests (22; 50; 60) and that are slidable along the arm rests (22; 50; 60), distal end portions of the slide members having belt guides through which webbing is passed; a belt anchor that is configured to be disposed on one seat width direction side of a lower portion of the seat back, and to which one end portion of the webbing is anchored; a retractor that is configured to be disposed on the other seat width direction side of a lower portion of the seat back and takes up the other end portion of the webbing passed through the belt guides on the both seat width direction sides, or a retractor that is disposed on the one seat width direction end side of an upper end portion of the seat back and takes up the other end portion of the webbing looped back in another belt anchor which is disposed on the other seat width direction side of the lower portion of the seat back and in which is looped back the webbing extending from the first belt anchor and passed through the belt guides on the both seat width direction sides; and a control unit that, in a state before an occupant is seated in the vehicle seat, causes the pair of arm rests (22; 50; 60) to be held in the storage position and causes the slide members (24; 52) to be held in a state in which the slide members (24; 52) have been slid further in a seat upward direction than a head rest, and that, in a state in which the occupant is seated, causes the pair of arm rests (22; 50; 60) to rotate from the storage position to the use position, causes the slide members (24; 52) to slide toward base sides of the arm rests (22; 50; 60), and causes a predetermined amount of the webbing to be taken up by the retractor.