An antenna and a communication device thereof are provided. The antenna includes at least one ground and at least one radiating portion. The ground is disposed on a dielectric substrate, and the radiating portion includes at least one signal source and at least one closed conductor loop. The closed conductor loop has a first coupling conductor portion and a second coupling conductor portion, and the closed conductor loop has a plurality of bending portions to form a three-dimensional structure, and a first coupling gap is formed between the first and the second coupling conductor portions. The closed conductor loop further has a feeding portion and a short-circuit portion to form a second coupling gap between them. The feeding portion is electrically connected or coupled to the at least one signal source, and the short-circuit portion is electrically connected or coupled to the ground.