An evaporated fuel treatment device includes a canister, an evaporated fuel outflow detecting means, a pressure sensor, a pressure change detecting means, and a pressure sensor failure determining means. The canister adsorbs evaporated fuel from a fuel tank, and purges the adsorbed fuel to an engine. The evaporated fuel outflow detecting means undergoes a change in a signal as the evaporated fuel flows out of the fuel tank. The pressure sensor detects an inner pressure of the fuel tank. The pressure change detecting means detects whether or not the pressure is in a static state. When the evaporated fuel outflow detecting means detects that evaporated fuel has flowed out of the fuel tank and when the pressure change detecting means detects that the pressure is in a static state, the pressure sensor failure determining means determines that the pressure sensor is out of order.