An index scan device comprising: an index storage unit that stores each index data for identifying each of a plurality of partial spaces, into which a multi-dimensional space mapped in a database is divided, in a manner such that each index data is associated with each page-identifying data for identifying a data page storing data belonging to each of the plurality of partial spaces; a search-space acquiring unit that acquires information on a search space in the multi-dimensional space corresponding to a search range of a query, or information on a partial search space in this search space; a search-point setting unit that sets, as a search point, a data point corresponding to at least one of a minimum and a maximum of values obtained by changing each data point in the multi-dimensional space to be one-dimensional, from among data points contained in the search space or the partial search space; an index searching unit that identifies, in the index storage unit, index data associated with a partial space containing the search point set by the search-point setting unit, and extracts page-identifying data associated with the identified index data, as page-identifying data corresponding to a partial space overlapping with at least part of the search space; and a search-area determining unit that estimates a boundary line passing through the search space or the partial search space and dividing the multi-dimensional space into the plurality of partial spaces, on the basis of identification information on the partial space obtained from the index data identified by the index searching unit, and determines, from among divided search spaces obtained by dividing the search space or the partial search space by the estimated boundary line, a divided search space excluding the partial space containing the search point as the partial search space wherein the multi-dimensional space is spatially divided using K-Dimensional -Tree; the multi-dimensional space is changed to be one-dimensional using a space-filling curve; a value obtained by changing each data point in the multi-dimensional space to be one-dimensional is expressed in binary form; the index storage unit sets, as the index data, a longest common prefix of the data points contained in each of the partial spaces; and the search-area determining unit estimates the boundary line to be located between a data point indicated by a value obtained by setting 1 for all digits from a last digit until a digit having 0 first appears in a direction toward the higher digit, and a data point indicated by a value obtained by adding 1 to said value, from among data points on each axis. an index storage unit that stores each index data for identifying each of a plurality of partial spaces, into which a multi-dimensional space mapped in a database is divided, in a manner such that each index data is associated with each page-identifying data for identifying a data page storing data belonging to each of the plurality of partial spaces; a search-space acquiring unit that acquires information on a search space in the multi-dimensional space corresponding to a search range of a query, or information on a partial search space in this search space; a search-point setting unit that sets, as a search point, a data point corresponding to at least one of a minimum and a maximum of values obtained by changing each data point in the multi-dimensional space to be one-dimensional, from among data points contained in the search space or the partial search space; an index searching unit that identifies, in the index storage unit, index data associated with a partial space containing the search point set by the search-point setting unit, and extracts page-identifying data associated with the identified index data, as page-identifying data corresponding to a partial space overlapping with at least part of the search space; and a search-area determining unit that estimates a boundary line passing through the search space or the partial search space and dividing the multi-dimensional space into the plurality of partial spaces, on the basis of identification information on the partial space obtained from the index data identified by the index searching unit, and determines, from among divided search spaces obtained by dividing the search space or the partial search space by the estimated boundary line, a divided search space excluding the partial space containing the search point as the partial search space wherein the multi-dimensional space is spatially divided using K-Dimensional -Tree; the multi-dimensional space is changed to be one-dimensional using a space-filling curve; a value obtained by changing each data point in the multi-dimensional space to be one-dimensional is expressed in binary form; the index storage unit sets, as the index data, a longest common prefix of the data points contained in each of the partial spaces; and the search-area determining unit estimates the boundary line to be located between a data point indicated by a value obtained by setting 1 for all digits from a last digit until a digit having 0 first appears in a direction toward the higher digit, and a data point indicated by a value obtained by adding 1 to said value, from among data points on each axis.