To provide a fuel vapor treating device capable of quickly separating fuel adsorbed in an absorbent from the adsorbent and returning the recovered fuel to a fuel supply system.

Fuel vapor vaporized in a fuel tank 11 is introduced into a canister case 13a through an introduction passage 12, and adsorbed in an adsorbent 19 within an adsorbent container 15 arranged in the canister case 13a. The adsorbent container 15 is forced to rotate with an electric motor 20 in timing every specified time during operation of the engine, and fuel adsorbed in the adsorbent 19 is separated by centrifugal force. Fuel separated from the adsorbent 19 is returned from the canister case 13a to the fuel tank 11 through a returning flow passage 12.