An antenna device includes: a substrate; micro-strip and grounding portions that are respectively disposed on opposite first and second surfaces of the substrate, the former including a signal-feed section for feeding of signals and a plurality of first connecting sections electrically connected to the signal-feed section; and a plurality of first loop antennas arranged along a peripheral edge of the grounding portion, each including a first radiator portion disposed on the first surface and electrically connected to a respective one of the first connecting sections, and a second radiator portion disposed on the second surface, electrically interconnecting the first radiator portion and the grounding portion, and cooperating with the first radiator portion to form a loop.