Provided are a deposition process monitoring system capable of detecting an internal state of a chamber in a deposition process, and a method of controlling the deposition process and a method of fabricating a semiconductor device using the system. The deposition process monitoring system includes a facility cover configured to define a space for a deposition process, a chamber located in the facility cover, covered with a translucent cover dome, and having a support on which a deposition target is placed, a plurality of lamps disposed in the facility cover, the lamps respectively disposed above and below the chamber, the lamps configured to supply radiant heat energy into the chamber during the deposition process, and a laser sensor disposed outside the chamber, the laser sensor configured to irradiate the cover dome with a laser beam and detect an intensity of the laser beam transmitted through the cover dome, wherein a state of by-products with which the cover dome is coated is determined based on the detected intensity of the laser beam.