1. A method for analyzing a microstructure of a porous body, comprising: using porous-body data in which positional information providing a position of a voxel of a porous body obtained by three-dimensional scanning is associated with voxel type information including information that allows determination as to whether the voxel is a spatial voxel representing a space or an object voxel representing an object, the method further comprising: (a) a step of defining an imaginary surface that is in contact with at least one object voxel present on a surface of the porous body, and identifying, as opening-related voxels, a spatial voxel that is in contact with the imaginary surface and a predetermined number or more of spatial voxels that continuously lie in a predetermined linear direction from the imaginary surface toward an inside of the porous body or identifying, as opening-related voxels, a predetermined number or more of spatial voxels that continuously lie in a predetermined linear direction from the imaginary surface toward an inside of the porous body; and (b) a step of analyzing a microstructure of the porous body on a basis of the opening-related voxels.