A hollow brick includes a bottom wall, two side walls projecting from the bottom wall, a plurality of intermediate walls projecting from the bottom wall between the side walls, a top wall opposite to the bottom wall and connecting the side walls and the intermediate walls, and a plurality of ventilation holes bounded by the bottom wall, the side walls, the intermediate walls and the top wall. The bottom wall has a plurality of foot portions projecting downwardly and spaced apart from each other. A bottom groove is formed between two adjacent ones of the foot portions.