Detection method and detection device

A detection device comprising:

• a sample container containing a sample including a complex that is formed by binding, to a target substance, a first substance immobilized to a metal particle with magnetism and a second substance labeled with a fluorescent material;
• a magnetic field applicator applying a magnetic field to the sample contained in the sample container, thereby the magnetic field moving the complex;
• a light source illuminating the sample contained in the sample container with excitation light of a predetermined wavelength, the excitation light causing the fluorescent material to emit fluorescence, the fluorescence being enhanced by localized surface plasmon resonance that is produced by the metal particle;
• an image captures capturing the enhanced fluorescence over time and obtaining two-dimensional images;
• and
• a detector detecting the target substance in accordance with a light spot included in each of the two-dimensional images,
• the metal particle including an inner core made of a magnetic material and an outer shell covering the inner core, the outer shell being made of a nonmagnetic metal material that produces the localized surface plasmon resonance.