1. A mesh number prediction method to be implemented in a computer, comprising: obtaining a mesh length for a case in which a mesh having an arbitrary shape is created by approximating an analyzing target by a three-dimensional mesh model that includes the analyzing target in its entirety, based on data of a three-dimensional surface model of the analyzing target; obtaining a mesh number of each of parts forming the analyzing target for a case in which a mesh having an arbitrary shape is created by approximating each of the parts by a three-dimensional mesh model, based on the mesh length; and obtaining a predicted total mesh number of the analyzing target in its entirety from a ratio of volumes by comparing a volume of the analyzing target in its entirety and a volume of each of the parts, based on the mesh number.