An information processing device comprising: an index generating means for generating index data that are distributedly stored into a plurality of servers, respectively, each of the index data being generated for each of data point information including metadata representing a characteristic of data to be searched, and each of the index data being associated with reference point information that are others of the data point information such that distances to the each data point information are between rings (411, 412, 413) around the data point information; and a communication cost storing means configured to store, for each of the servers storing the respective index data, communication cost information representing a cost that costs based on a time to communicate with the server, wherein the index generating means is configured to select the reference point information to be associated with specific one of the data point information, based on the communication cost information of the server storing the index data corresponding to the reference point information, and wherein the index generating means is configured to: exclude one of reference point candidate information from among the reference point candidate information that are the others of the data point information to become candidates of the reference point information for the specific one of the data point information and calculate, with reference to one of remainder of the reference point candidate information, a coordinate point such that coordinates are distances of others of the reference point candidate information; calculate a volume of a polyhedron such that each of vertexes is the coordinate point calculated with reference to each of the remainder of the reference point candidate information; and select a predetermined number of the reference point information to be associated with the specific one of the data point information, based on the calculated volume and the communication cost information of the server storing the index data corresponding to the excluded one of the reference point candidate information. an index generating means for generating index data that are distributedly stored into a plurality of servers, respectively, each of the index data being generated for each of data point information including metadata representing a characteristic of data to be searched, and each of the index data being associated with reference point information that are others of the data point information such that distances to the each data point information are between rings (411, 412, 413) around the data point information; and a communication cost storing means configured to store, for each of the servers storing the respective index data, communication cost information representing a cost that costs based on a time to communicate with the server, wherein the index generating means is configured to select the reference point information to be associated with specific one of the data point information, based on the communication cost information of the server storing the index data corresponding to the reference point information, and wherein the index generating means is configured to: exclude one of reference point candidate information from among the reference point candidate information that are the others of the data point information to become candidates of the reference point information for the specific one of the data point information and calculate, with reference to one of remainder of the reference point candidate information, a coordinate point such that coordinates are distances of others of the reference point candidate information; calculate a volume of a polyhedron such that each of vertexes is the coordinate point calculated with reference to each of the remainder of the reference point candidate information; and select a predetermined number of the reference point information to be associated with the specific one of the data point information, based on the calculated volume and the communication cost information of the server storing the index data corresponding to the excluded one of the reference point candidate information.