EVAPORATED FUEL TREATMENT APPARATUS

In an evaporated fuel treatment apparatus, a controller performs first purge concentration determination control by gradually increasing a purge flow rate in increments of a predetermined amount and detect a purge concentration based on a detection value of the pressure sensor. As the first purge concentration determination control, the controller performs a control to prohibit changing of an operating state of the purge pump or changing of an open state of the purge valve until a detected concentration determination time at which a variation range of the purge concentration detected based on a detection value of a pressure sensor becomes equal to or less than a predetermined value.