To recognize leucocyte, to determine periodontal disease based on it, and to use a periodontal pocket as a noninvasive experiment place of infection, inflammation, or immunity.

This leucocyte measurement device, mainly using a leucocyte group analyzing means, performs a determining diagnosis of a periodontal disease, and solves the problem. Further, the leucocyte measurement device includes a new neutrophil searching means, an old neutrophil searching means, and a vector field sampling means. The vector field sampling means employs a piping means.