To detect the generation of a biological reaction using a superparamagnetic particle, or to determine result thereof quantitatively.

The same biomolecule of a member of a biological coupling pair is coupled or adsorbed onto the superparamagnetic particle to contact with a liquid or solid sample wherein the molecule of a biological coupling partner is known to be contained in the biomolecule, or is estimated therein. The coupling object or the adsorption object is brought into contact with the liquid or solid sample for a sufficient time to form a firmly coupled three-dimensional block containing the connected biomolecule and the coupled superparamagnetic particle. The block is exposed to a magnetic field of an experiment equipment for the shortest time required for inducing magnetization in the superparamagnetic particle, and the magnetic field is removed immediately. The block exhibits the nonpermanent measurable magnetization lasting for at least 20 minutes after exposed to the magnetic field. In this method, the bioreaction is detected using a correlation between magnetic signal intensity and one quantitative determination concentration or the number of the biomolecule.