A seat belt apparatus simplifying an operation of mounting tongues to left and right respective buckles is provided. In the seat belt apparatus, a second tongue is held by a second tongue containing portion provided at a first buckle, and a first tongue is held by a first tongue containing portion provided at a second buckle. When mounting a first and second shoulder belt, and a first and second lap belt, when both of the first buckle and the second buckle are pulled to a front side of an occupant and an inserting hole of the first buckle and an inserting piece of the first tongue are opposed to each other, an inserting piece of the second tongue and an inserting hole of the second buckle are opposed to each other. When the inserting piece of the first tongue is inserted to the inserting hole of the first buckle, the inserting piece of the second tongue is inserted to the inserting hole of the second buckle.