The present invention relates to a group control elevator system which has been adjusted to operate in response to a state of utilizing elevator cars. In a group control elevator system which carries out a control of allocating elevator cars to elevator car calls for serving many floors by using an evaluation function having a plurality of variable parameters, targets for elevator control performance are inputted, a traffic flow to which elevator car demand belongs is judged, variable parameters to be adjusted which have been set in advance for each combination of said targets and traffic flows are stored, stored variable parameters are adjusted, adjustment sequence of variable parameters to be adjusted is stored, and a plurality of variable parameters are sequentially adjusted according to the stored sequence. By the above arrangement, only desired parameters to be adjusted are selected and adjusted out of a plurality of variable parameters for desired targets and traffic flows. Accordingly, an increase in time required for adjustment can be restricted even if there has been an increase in the number of variable parameters to be adjusted.