1. A method for predicting a modal damping ratio of a composite head comprising two or more kinds of materials comprising a first material and a second material, the method comprising the steps of: presuming at least a coefficient Px of a generalized Maxwell model M1 in the first material using a known material damping ratio ζ1; obtaining a calculation model of the head using the generalized Maxwell model M1; and calculating the modal damping ratio of the head based on analysis of the head using the calculation model.