The molecular information providing system of the invention has the terminal units to including molecular structure input/output means, and a molecular information providing apparatus connected via a network to the terminal units and including a database storing a molecular structure, an intermediate representation generated from the molecular structure, and a characteristic decided depending on the molecular structure. The molecular information providing apparatus comprises a coordinate system transforming part for calculating the principal axes of inertia from an atomic arrangement notation specifying the molecular structure, and registering in the database an intermediate representation that is a coordinate transformation of the atomic coordinates into a coordinate system in the directions of the principal axes of inertia, and a retrieval executing part for retrieving the molecular structure stored in the database, employing the intermediate representation.