A mobile communication device includes an antenna structure having a dielectric substrate and an antenna. The dielectric substrate includes a ground portion, a first non-ground portion, and a second non-ground portion. The ground portion further includes a main ground and a protruded ground electrically connected to the main ground and extending between the first non-ground portion and the second non-ground portion. The first non-ground portion and the second non-ground portion are separated by the protruded ground. One edge of the protruded ground aligns with one edge of the dielectric substrate. The antenna includes a feeding portion located in the first non-ground portion and a radiating portion extending over the protruded ground and having a first end located in the first non-ground portion and electrically connected to the main ground and a second end of the radiating portion is located in the second non-ground portion and electrically connected to the main ground. There is a coupling gap between the radiating portion and the feeding portion in the first non-ground portion, and the radiating portion is excited by the capacitive coupling effect from the feeding portion.