A multi-band antenna includes a dielectric substrate, and a main antenna member and a metal piece disposed on the dielectric substrate. The main antenna member includes a feed-in portion for feeding with a radio frequency signal, a first conductor arm connected to the feed-in portion and adjacent to a first side edge of the dielectric substrate, a second conductor arm connected to the feed-in portion and having a length shorter than that of the first conductor arm, a third conductor arm connected to the feed-in portion, a fourth conductor arm extending along the third conductor arm, and a grounding portion adjacent to the feed-in portion. The metal piece is disposed at the first side edge and connected to the fourth conductor arm, resonates and couples with the first conductor arm to form a first radiator section, and cooperates with the fourth conductor arm to form a second radiator section.