Disclosed is a convertible top assembly for a vehicle, which comprises a pair of reinforcing plate members 20 each attached to an inner surface of a lower region in a corresponding one of right and left lateral edges of a convertible top 3, and connection means X (plate spring 28) for connecting between a main link 6 and each of the reinforcing plate members 20, whereby the rigidity of the lower region in each of the right and left lateral edges of the convertible top 3 is increased to ensure a sufficient sealing between the convertible top 3 and a vehicle body 2 in a closed position of the convertible top 3 in a simplified structure.