To provide a simple restructuring device for a stereoscopic image of a three- dimensional space distribution of a powder in a fluid and for a space distribution of the powder, by which a short continuous phenomenon such as a space movement of a powder can be followed, of which a processing time is short and the amount of a record medium is little.

This device is composed of a projection means α for introducing parallel rays each generated from a plurality of positions to a region to be visualized in which a powder is located and transmitting them through the region, a projection image processing means β for taking a photograph of a projection image projected by the projection means αto image-process it, a stereoscopic image construction means γ of a three-dimensional space distribution, for determining a powder concentration distribution of the powder at arbitrary coordinates as a function of the components of projection coordinates to restructure it as for whole region to be visualized, based on a plurality of data each obtained by the projection image processing means β at the same time, and a construction means δ of a powder traveling speed distribution, which carries out the stereoscopic image construction means γ at two consecutive times to represent each cross correlation of the powder space distributions of the two consecutive times by a distribution of vector values.