The invention discloses an embedded flat heat collecting roof/wall surface, which belongs to the integrated technology of solar buildings and solves the problem that the conventional flat heat collector has single function. The embedded flat heat collecting roof/wall surface comprises a back plate, an outer frame body, a heat collecting plate, a cover plate and a heat insulation water tank, wherein the back plate and the cover plate are used as the back and front of the outer frame body respectively, and the back plate, the cover plate and the outer frame body form a sealed hollow cavity together; and the heat collecting plate is arranged inside the hollow cavity. The embedded flat heat collecting roof/wall surface is characterized in that the back plate is provided with a working medium inlet and a working medium outlet; one end of the working medium inlet is communicated with the lower end of the heat collecting plate, while the other end is communicated with the heat insulation water tank through a liquid down pipe; and one end of the working medium outlet is communicated with the upper end of the heat collecting plate, while the other end is communicated with the heat insulation water tank through a steam rising pipe. The embedded flat heat collecting roof/wall surface has a reasonable structure, realizes the functions of buildings such as heat preservation, heat isolation, rainwater prevention and the like, also can be used as a heat collector for realizing the functions of the buildings such as warming, dehumidifying and the like, and has higher practical value.