To a canister assembly to be installed in a vehicle body having a differential device mounted on a rear part thereof without reducing the space above a floor panel while ensuring an adequate adsorption chamber volume. The canister assembly (22) comprises a first adsorption chamber (31) for adsorbing fuel vapor introduced from a fuel tank (8); a second adsorption chamber (32) for adsorbing fuel vapor introduced from the first adsorption chamber; and a chamber communication pipe (46) for communicating the first adsorption chamber with the second adsorption chamber; wherein the first adsorption chamber and second adsorption chamber are provided separately from each other on either side of the differential device.