1. A method for controlling a molecular information providing apparatus that is an information processing unit including a database for retrieving a characteristic decided depending on a molecular structure on a basis of said molecular structure, said method comprising: using a processor to perform steps comprising: receiving a processing request that requests a computation of a molecular orbital corresponding to said molecular structure; calculating principal axes of inertia from an atomic arrangement notation specifying said molecular structure, and registering said principal axes of inertia in a memory; determining how close a principal moment of inertia of said molecular structure is to said principal axes of inertia; reading out data of the principal axes of inertia from said memory, and registering in said database an intermediate representation that is a coordinate transformation of atomic coordinates of said molecular structure into a coordinate system in directions of said principal axes of inertia; computing said molecular orbital, when an estimated computation time for said processing request does not exceed a threshold value; and retrieving the molecular structure from said database, employing said intermediate representation, and registering the molecular structure in the memory, when said estimated computation time exceeds the threshold value.