PURPOSE: To simultaneously perform processings from the input of data to the design and update by eliminating manual and troublesome calculation works in a water-distribution pipe network simulator calculating the pressure and flow rate, etc., of the water-distribution pipe network of water service and simulating the status within the pipe network.

CONSTITUTION: This simulator is provided with a drawing input part 1 having a drawing reading function, a drawing recognition function, a drawing function and a drawing joint function and preparing the graphic database of water service facilitates from an inputted drawing, a database control part 2 fetching the attribute data of the graphic database and design result and editing the graphic database, a pipe network design part 3 calculating the pressure and the flow rate of a water-distribution pipe network by defining the water level of water distributing reservoir, node outflow, pipe diameters and connection information, etc., as conditions based on the data of the graphic database, and preparing and editing a model for design and a display part 4 performing a color display and a graphic display of the calculation result data of the pressure and the flow rate and the comparison result of this data and measured data.