The present invention provides an antenna diversity apparatus and an antenna diversity method. The antenna diversity apparatus comprises: a plurality groups of antennas, a switching unit, a demodulating unit, an antenna switch selecting unit, and a control unit, wherein each group of the plurality groups of antennas comprises at least an antenna, and the control unit can comprises: a receiving signal quality detecting unit, a packet detecting unit, and an antenna decision unit. The antenna decision unit can be realized by hardware, firmware, or software, and the antenna switch selecting unit can be realized by hardware. The antenna diversity apparatus and the antenna diversity method provided by the present invention can switch antennas fast to avoid the defect of occurring burst error to reduce transmitting data rate, and switch to proper antennas fast when variation of the data transmission channels occurs.