A device with a memory function for detecting closure of vehicle doors and the method thereof is disclosed. Before a vehicle door is open, a detecting signal near the outer side of the door is emitted and its detection status is recorded. When the vehicle door is to be closed, a first detecting signal is emitted from the door frame top downwards and a second detecting signal is emitted near the outer side of the door. If the first detecting signal indicates that a person is at the door or the second detecting signal indicates that a person exists on the outer side of the door by comparison with a precious record, then the door is prohibited from being closed. Otherwise, the door can be closed. This automatic detection method can prevent the driver from accidentally hurt passengers by carelessly closing the doors.