A reflector structure is configured to connect an antenna. The antenna has an excitation source. The reflector structure includes a metal substrate, at least one first flat plate and a second flat plate. The metal substrate is configured to reflect the radiation of the antenna. The at least one first flat plate is disposed on the metal substrate. The second flat plate is floated to the metal substrate along a virtual normal and completely separated from the at least one first flat plate to form a closed slot. A cavity is formed by the metal substrate, the at least one first flat plate and the second flat plate and communicated with the closed slot. The excitation source is projected onto a plane to form an excitation source region. The excitation source region is located in the second flat plate.