Abstract: A built-in multi-band mobile phone antenna includes: a meandering conductive body having a signal feeding point, and first and second meandering conductive portions disposed at two sides of the signal feeding point; a conductive flat first radiating plate in electrical connection with the first meandering conductive portion and tuned to a low frequency range; an elongated conductive flat second radiating plate in electrical connection with the second meandering conductive portion and a grounding point and tuned to a high frequency range; and a conductive flat parasitic plate in electrical connection with the grounding point so as to widen the bandwidth of the antenna. The conductive body, the first and second radiating plates, and the parasitic plate define cooperatively a plate-shaped accommodating space thereamong for receiving a plate-shaped electronic element.