The present invention discloses an automatic parking system including an in-out space, a plurality of parking spaces arranged at multiple parking levels, a pickup machine, and a lifting tunnel with a lifting device disposed therein. The pickup machine includes a frame which includes a first frame and a second frame, a first pickup device and a second pickup device. The first pickup device is configured to move a loading board onto the first frame or out from the first frame. The second pickup device is configured to move the loading board onto the second frame or out from the second frame. The lifting device is configured to convey the pickup machine up and down in the lifting tunnel. The present invention also discloses a parking and unparking method of the automatic parking system. The parking and unparking efficiency of the automatic parking system of the present invention is greatly improved.