To provide a hot water and steam generation device capable of generating hot water and steam with the high use efficiency of the combustion energy of plants and trees, and being easily assembled in a site by carrying lightweight members.

Three or more of unit members in total each having the roughly flat rectangular parallelepiped shape as its outer shape, having a connectable configuration, having a space capable of storing water, provided with two or more injection/discharge ports to an internal space on its outer face, and further having two or more tubular through holes for connecting outer faces and inner faces are used at a wall and a ceiling, a perforated steel plate 52 is disposed at an interval from a fire grate 51 and a wall inside, and the insertion of an ignition burner at starting combustion, and the monitoring of an internal state are performed by utilizing the tubular through holes, and hot water and steam can be generated by using a combustion furnace 1 provided with a hot water-steam generation pipe 61 for generating the hot water or steam, an air supply pipe 62 for combustion, a stirring machine 63 for a combustion material, a stirring device 64 for the combustion material and the like.