To provide a method for estimating a packing structure of a π-conjugated molecule without forming various initial structural models, an apparatus and the like.

The apparatus 1 for estimating a packing structure to which the method for estimating a packing structure of such a molecule is applied has a molecular model preparation section 21 to prepare a molecular model of the π-conjugated molecule whose packing structure comes to an estimation target, a unit cell preparation section 22 to obtain a repeating unit by arranging a plurality of the molecular models on the same plane to prepare a unit cell reflective of the repeating unit, an initial structure preparation section 23 to arrange the molecular model in the unit cell, and a structure-determination section 24 to render the molecular model-arranged unit cell structure a chemically stabler packing structure by the molecular dynamics method.