A heat-collecting kiln device includes a housing assembly including a single housing or a plurality of housings having a same height or different heights, with the housings stackable one upon another. A top lid is mounted on a top of the housing assembly to seal the housing assembly and includes an observation hole. A base is mounted to a bottom of the housing assembly to seal the housing assembly. A cover is mounted to the top lid to seal the observation hole. The cover is removable to reveal the observation hole. The heat-collecting kiln device further includes a net and at least one leg. Each housing is comprised of four modular elements each having a mortise engaged with a tenon of another modular element. One of the modular elements includes a temperature detection hole.