PROBLEM TO BE SOLVED: To provide a biosensor that detects a biomaterial at low cost and with high sensitivity, without using a high-sensitivity and expensive sensor, and that enables quantitative measurements. SOLUTION: The marker for the biosensor includes a plurality of magnetic particulate seeds 10, fixed in the vicinity of a detection region of the biosensor along with the biomaterial 4; and at least one target magnetic particulate 20 which is relatively larger than the magnetic particulate seeds. The target magnetic particulate 20 is adsorbed by a plurality of magnetic particulate seeds 10, by applying an external magnetic field from a magnetic field generating source 30. The biomaterial is detected, by detecting the marker comprising the adsorbed magnetic particulate seeds 10 and target magnetic particulate 20. COPYRIGHT: (C)2009,JPO&INPIT
