1. A parameter configuration apparatus for externally configuring a value of an image processing parameter used in an image input device which outputs image data resulted from image processing according to the image processing parameter, comprising: a change request unit which transmits a change request to change the value of the image processing parameter to a designated value to the image input device; a reception unit which receives the image data from the image input device; a display unit which displays the received image data; and a control unit which controls the change request unit to sequentially transmit a plurality of change requests to change the value of the image processing parameter to values respectively different from the designated value, control the reception unit to sequentially receive a plurality of image data reflecting the plurality of change requests, control display unit to display the plurality of image data, and control the change request unit to transmit the change request to change the value of the image processing parameter to a value corresponding to one of the plurality of image data selected by a user, as the designated value.