1. A characteristic control device which is provided with: a basic control module which determines the amount of control used to control the output of a control subject based on predetermined input data and control parameters which relate output to the control subject to the input data and which controls the characteristics of the control parameters, a characteristic storage mechanism for storing the basic control parameters, and a characteristic automatic modification mechanism which determines, in accordance with predetermined conditions, and automatically modifies, the control parameters which are applied to the basic control module based on the basic control parameters stored in the characteristic storage mechanism and the input data.