A hot water boiler with double combustion chambers comprises a boiler body. A water heating chamber, the first combustion chamber, the second combustion chamber, a smoke collection chamber, an ash chamber and a smoke filter box are arranged in the boiler body. The water heating chamber is arranged at the upper left end inside the boiler body. The first combustion chamber is arranged at the lower end of the water heating chamber. The smoke collection chamber is arranged at the right ends of the water heating chamber and the first combustion chamber. The ash chamber is arranged at the lower ends of the first combustion chamber and the smoke collection chamber. The second combustion chamber is arranged in the middle of the interior of the water heating chamber. A smoke box is arranged inside the smoke collection chamber. The interior of the smoke box is composed of an upper cavity and a lower cavity. The upper right end of the first combustion chamber is connected with the lower cavity through a first smoke conveying pipe. The lower right end of the second combustion chamber is connected with the upper cavity through a second smoke conveying pipe. The upper cavity is connected with the smoke filter box through a heat exchange smoke pipe. The lower cavity is connected with the smoke filter box through a heat exchange smoke pipe. The hot water boiler is provided with the two combustion chambers, the heat exchange area is enlarged, the heat efficiency is improved, and the water heating speed is increased.