A mask manufacturing system and a mask data creating method reusing data for processing information and environment in the past to reduce a photomask developing period, and a manufacturing method of a semiconductor device are disclosed. According to one aspect of the present invention, it is provided a mask manufacturing system comprising a storage device storing processing data for semiconductor integrated circuits processed in the past, a plurality of operation processing modules, a module selecting section selecting at least one operation processing modules, an optical proximity effect correction section executing optical proximity effect correction to a processing object data and generating a correction data by utilizing past correction information applied for a stored data equivalent to the processing object data, a converting section converting the processing object data into mask data, and a drawing system drawing a mask pattern based on the mask data.