The invention relates to a sealed expansion compartment. The sealed expansion compartment has the advantages that novel sealed spaces can be formed by opened rear doors of a vehicle and a sealing flexible canopy, so that the internal volume of the vehicle can be enlarged, and rest spaces can be provided for passengers; the sealing flexible canopy (2) is mounted between the rear door (1) and a rear door opening (3), so that purposes of sealing the novel spaces formed after the rear door (1) is opened and expanding the internal spaces of the vehicle can be achieved.