A vehicle steering control unit which can implement various type of self-tuning in accordance with various properties of an objective vehicle is realized. ECU includes a control information acquiring part 501 which acquires control information which is information relating to the controlling of steering of the vehicle, a parameter value calculation part 502 which calculates after-change values for parameters whose values need to be changed in various steering control parameters based on the control information acquired by the control information acquiring part 501, and a parameter value rewrite part 503 which rewrites the values of steering control parameters. The control information includes information representing system properties of an objective vehicle, information retained by the chassis control system, and information on elements which make up a steering system which is installed on the objective vehicle.