In a measuring apparatus for biomolecule interaction, a fine particle sensor surface is dipped in a buffer solution in a reaction vessel to conduct spectral measurement by way of optical fibers. The buffer solution in the reaction vessel is made to enter an upper reaction vessel and discharged from a flow channel. Air is injected from a flow channel to inject a specimen from the discharge port to the reaction vessel. Then the specimen is sucked into the reaction vessel and brought into contact with the sensor surface where a ligand and an analyte in the specimen are bonded. Bonding is measured by a spectrophotometer through the optical fibers. A buffer solution is injected from the injection flow channel into the reaction vessel and the specimen is discharged out of the flow channel. The dissociation process in which the biomolecules are dissociated along with lowering of the concentration is measured.