a fuel vapor capturing canister includes a casing formed into the shape of a cylinder and accommodating an adsorbent material . a partition member divides the activated carbon into lower and upper layers . the partition member includes a cross rib and upper and lower walls sandwiching the rib . one of four pieces of the cross rib is connected to the inner peripheral wall of the partition member . two chambers located at both sides of the piece connected to the inner peripheral wall of the partition member communicate with each other through a communicating path defined between the other pieces of the rib and the inner peripheral wall of the partition member . one of the two chambers has in its underside openings communicating with the lower activated carbon layer while the other chamber has in its top openings communicating with the upper activated carbon layer . the fuel vapor flows between the two layers of activated carbon . since the communicating path between the layers of activated carbon is long , the fuel vapor capturing performance can be improved .