A method for determining a connection state of an engine clutch includes: a stroke sensing operation of sensing, by a controller, a change of an actuator stroke of the engine clutch; a first pressure comparing operation of determining whether or not an actuator pressure of the engine clutch exceeds a first set pressure and is then changed to below the first set pressure when the actuator stroke is increased; a torque comparing operation of comparing transfer a torque of the engine clutch with a set torque when the actuator pressure exceeds the first set pressure and is then operated to below the first set pressure; and an open determining operation of determining that the engine clutch is in an open state when the transfer torque of the engine clutch is the set torque or less.