High density arrays of quantum dots (QDs) can easily be grown by ‘self-assembled’ methods. However, the precise mechanism of ‘self-assembled’ is not well understood, which hampers the control over QD size, density and distribution for particular applications. Therefore, in-situ evaluation technique for observing the growth process is necessary and indispensable. STM is a good technique to observe the surface in atomic level but it prevents vibrations and material depositions. So, usually its observation is made after transporting the sample from MBE growth chamber to the STM through a gate valve, resulting that the temperature of the sample is returned to room temperature. Since the real in-situ observation cannot be done with this ordinary method, we develop “STMBE” system in which the STM is placed completely inside MBE growth chamber, and with this system, the surface structure is analyzed centering on the in-situ STM observation of the InAs QD self-assemble process on GaAs(001).