1. A virtual radio map constructing method, comprising: converting first and second received signal strengths (RSS values) obtained from two access points adjacent to each of a plurality of access points disposed in a target space into first and second RSS values of a linear unit; respectively dividing first and second distances between an access point of the plurality of access points and the two access points adjacent thereto in an exponential interval, and respectively dividing the converted first and second RSS values in the exponential interval; generating a plurality of virtual training points in the target space by using a plurality of points divided in the exponential interval between the access point and the two adjacent access points, and respectively obtaining RSS values of the plurality of virtual training points by using first and second RSS values corresponding to the virtual training point; and respectively obtaining RSS values of reference points by using RSS values of at least one virtual training points existing within a reference distance from each of the reference points arranged in an equal interval in the target space.