An object of the present invention is to provide a new form of adsorbent suitable for a motor vehicle canister. An activated carbon fiber sheet satisfies one or two or more of conditions for indices, such as a specific surface area, a pore volume of pores having a given pore diameter, and a sheet density. An embodiment, for example, may have: a specific surface area ranging from 1400 to 2200 m2/g; a pore volume ranging from 0.20 to 1.20 cm3/g for pores having pore diameters of more than 0.7 nm and 2.0 nm or less; and a sheet density ranging from 0.030 to 0.200 g/cm3.