An interlaced array antenna includes first and second groups of antenna units, which are of the same size in the same group and different sizes in different groups. Each antenna unit is polygon-shaped with even-numbered edges, and has feed-in terminal and coupling terminal at two corners. A preceding one and a succeeding one of the antenna units included in the first group are interconnected via a specified one of the antenna units in the second group. An input signal is transmitted through the feed-in terminal and then the coupling terminal of the preceding antenna unit, the feed-in terminal and then the coupling terminal of the specified antenna unit, and the feed-in terminal and then the coupling terminal of the succeeding antenna unit in sequence. Configurations of adjacent two antenna units in the same group are identical once one of them is flipped about the x-axis.