A spatial information visualization apparatus in an embodiment includes a storage, a vacant space processor, a spatial information generator, and an image generator. The storage stores design dimensions of a target space, and measurement information indicating coordinates of a measurement point of the target space measured by scanning the target space from a plurality of different reference points in the target space, for each of the reference points. The vacant space processor specifies a vacant space existing in the measured space stored in the storage, on the basis of the coordinates of the measurement point of the target space included in the measurement information read for each of the reference points from the storage, coordinates of the reference point, and the design dimensions of the space.