A system is provided for adjusting a photo-exposure time of a manufacturing apparatus for semiconductor devices. The system for adjusting the photo-exposure time includes a photo-exposure unit whose photo-exposure time is adjustable according to one or more adjustment signals, a pre-exposure step influence prediction unit that obtains pre-exposure step processing information and extracts parameters that may influence a resulting pattern during photo-exposure, and provides this information as feed forward data, an inspection unit that checks processed steps during a certain period after photo-exposure and provides an inspection value as a feed back data, and a central processing unit that receives the feed forward and feedback data and, by means of a predetermined calculation method, generates the one or more adjustment signals, which are used to adjust the photo-exposure time.