Fuel vapor treatment canister

A fuel vapor treatment canister for controllably storing and releasing fuel vapor from a fuel tank and the like of an automotive vehicle. The fuel vapor treatment canister comprising a casing having first and second end walls between which an inside space is formed. The first end wall has a first opening in communication with a fuel tank, and a second opening in communication with an air intake passage of an engine. The second end wall has a third opening in communication with the atmosphere. The inside space includes first and second chambers. The first chamber is located closer to the first end wall than the second chamber. A partition wall is disposed to divide the inside space into the first and second chambers. The partition wall structure has an air permeability and a heat insulating ability higher than that of metal. A first fuel vapor adsorbing material is disposed in the first chamber. A second fuel vapor adsorbing material and a heat-accumulative material are disposed in the second chamber. The heat-accumulative material is larger in specific heat than the second fuel vapor adsorbing material.