A device and a method for automatically restoring a seatback is provided in which a seatback is electrically deployed at a predetermined angle by being interlocked when a seat of a vehicle is moved to a predetermined position to facilitate a passenger to get into and out of the vehicle. The device includes a seat cushion, a seatback installed in the seat cushion to be adjustable in angle, a seat rail, and a seat track slidably installed in the seat rail. A seat position detection sensor detects a position of the seat track and a seat position detection member operates the seat position detection sensor. A seatback angle adjustment motor adjusts an angle of the seatback. When the seat position detection sensor detects that the seat track reaches a predetermined operating position, the seatback angle adjustment motor deploys the seatback.