A dual-band antenna and a wireless communications device are disclosed. The dual-band antenna includes a first antenna arranged on a first printed circuit board (PCB), a second antenna arranged on a second PCB, and a reflection panel. An operating frequency band of the first antenna is a first frequency band. An operating frequency band of the second antenna is a second frequency band. The first frequency band is higher than the second frequency band. The second PCB is disposed between the first PCB and the reflection panel. The reflection panel includes an artificial magnetic conductor. A resonant frequency band of the artificial magnetic conductor includes the second frequency band. The first frequency band is outside the resonant frequency band. The dual-band antenna has a small size.