An evaporated fuel treatment device is provided in a canister including first to third chambers. The first chamber is provided with an inflow port and an outflow port at an end part thereof, and is connected to the second chamber. The evaporated fuel treatment device is configured as the third chamber of the canister. The third chamber has disposed therein activated carbon as an adsorbent material. The side connected to the second chamber in the third chamber is defined as second chamber side, and the side opposite to the second chamber side is defined as atmosphere side. An atmosphere port is provided at an end part on the atmosphere side of the third chamber. The third chamber is provided with a highly adsorptive layer and a low adsorptive layer which are aligned from the second chamber side to the atmosphere side.