A dual-band dual-antenna structure is provided. The dual-band dual-antenna structure comprises a substrate, a first antenna and a second antenna. The substrate comprises a first signal transport layer and a second signal transport layer, wherein the second signal transport layer is not coplanar with the first signal transport layer. The first antenna is disposed on the first signal transport layer and comprises a first U-shaped radiation element and a first polygon radiation element. The first polygon radiation element is disposed in an opening of the first U-shaped radiation element. The second antenna is disposed on the second signal transport layer but does not overlap under the first antenna. The second antenna comprises a second U-shaped radiation element and a second polygon radiation element. The second polygon radiation element is disposed in an opening of the second U-shaped radiation element.