A communication device including a multilayer circuit board and an antenna structure therein is provided. The multilayer circuit board has at least a first plane, a second plane, and a third plane. A ground plane is disposed on one of the planes, and the ground plane is in proximity to a clearance region of the multilayer circuit board. An antenna structure is disposed in the clearance region. The antenna structure includes a first metal portion and a second metal portion. The first metal portion is coupled to a signal source through a feeding portion. The second metal portion includes at least a first line segment and a second line segment. The first line segment and the second line segment are disposed respectively on any two planes of the multilayer circuit board. The first metal line and the second metal line forms a loop structure through two conductive vias.