Abstract: A seat of a bicycle including a pair of rods disposed on the bottom, a plate disposed above the rods, a bracket disposed below the rods and fixed to the plate so as to fix the rods between the plate and the bracket, the bracket including two flanges formed on the bottom portion, a bag including a member disposed on the upper portion and having a pair of channels for engagement with the flanges of the bracket so that the member can be coupled to the bracket and so that the bag can be coupled to the seat.