PURPOSE: To provide the CAD system which can reflect an updating work by all terminals on a new drawing file on a host, even if plural terminals update simultaneously the same drawing and execute a retaining operation by an arbitrary timing, at the time of retaining the drawing.

CONSTITUTION: In plural terminals 2, 3,... connected to a host 1 through a communication circuit, a drawing updating part 5 for receiving input data from an input part 4 being a function of a conventional terminal and updating an old drawing to a new drawing, a drawing file storage part 6 for storing the updated new drawing, a display part 7 for displaying the drawing, a communication part 8 for executing a communication to the host 1, and also, an additional element storage part 9 for storing an additional element added to the drawing at the time of editing newly the drawing are provided, and in the host 1, a drawing file retaining part 10 being a function of a conventional host and a communication part 11, and also, a drawing updating part 12 for receiving plural additional elements to the same drawing transmitted newly from plural terminals 2, 3,..., and updating the old drawing stored in the drawing file retaining part 10 are provided.