The disclosure provides an antenna module adapted for an electronic device having a metal casing. The antenna module includes an antenna structure and a slot structure. The antenna structure includes a radiation portion, a feeding portion, a ground portion and an extension portion, wherein the feeding portion, the ground portion and the extension portion are connected to the radiation portion. The slot structure has an open end and a closed end, wherein the open end of the slot structure is adjacent to the extension portion of the antenna structure. The antenna structure is excited and resonates to generate a first antenna resonant mode, and the slot structure is coupled to the antenna structure and resonates to generate a second antenna resonant mode.