PURPOSE: To determine a specimen cell object by comparing the optical density of the stain specimen cell object with the optical density of a stain reference substance containing the known amount of a substance to be determined.

CONSTITUTION: A reference substance with a physical characteristic for connecting the reference substance that contains a known amount of DNA and is proportional to the connection between a dye and the DNA is supplied to a reference region 28 of a slide 10 with a reference region 28 and a specimen cell object region 30. Then, a specimen cell object 32 is supplied onto the specimen cell target region 30. Then, both the reference substance and the specimen cell object 32 are stained simultaneously within a specific time by an effective amount of dye water solution for giving an optical density that is a primary function of the stain concentration the reference substance after staining to the reference substance. Then, after the staining, the optical density of the reference substance and that of the specimen cell objet 32 are measured. Then, by comparing the optical density of the reference substance with that of the specimen cell object 32, the DNA content of the specimen cell object 32 can be calculated as an absolute DNA weight.