Further miniaturization of the diaphragm for capacitive pressure sensor requires thinner structures to deform micro diaphragm sufficiently by small differential pressure. Since stiffness of thinner structures decrease, the influence of internal stress introduced during processing cannot be ignored. In this paper, we proposed methods of controlling the internal stress for micro diaphragm using thin film metallic glasses (TFMGs). We fabricated micro diaphragms using Ru67Zr25Al8 [at.%] TFMGs. The TFMGs were fabricated by a r.f. sputtering system, and then as sputtered TFMGs had compressive internal stress. Subsequently, the as-sputtered TFMGs on Si substrate were annealed at 315-440°C for 5 minutes in vacuum. After annealing, micro diaphragms were fabricated by etching Si substrate using a reactive ion etching system. Although annealing temperatures were lower than glass transition temperature, initial internal stress was relaxed partially by the structural relaxation of the TFMGs during annealing process. While the tensile thermal stress was induced during cooling process at the interface between the substrate and TFMG. Although micro diaphragm was not induced thermal stress at interface between the substrate and TFMG, the tensile stress applied to diaphragm in the radial direction at the edge. When annealing temperatures were between 320°C and 340°C, the internal stress changed from compressive to tensile. A flat diaphragm was obtained when annealed at 330°C or higher. The pressure sensor modeled by diaphragm annealed at 340°C and the virtual electrode plate showed a linearity of 6.48 [%F.S.]. By proposed method, we succeeded the flat diaphragm and showed the method of tension control of the diaphragm.