Concentration measurement method

A concentration measurement method for measuring a concentration of an analyte in a measurement solution containing the analyte having reducing action, the method comprising:

• a first step of preparing the measurement solution containing the analyte which is an object to be measured;
• a mixing step of, after the first step, preparing a mixture solution by mixing a metal ion solution containing metal ions, a pH adjusting agent, and the measurement solution containing the analyte;
• a metal microstructure generation step of, after the mixing step, generating a metal microstructure on a support by reducing the metal ions in the mixture solution by the reducing action of the analyte in the mixture solution, the metal microstructure being a structure in which aggregations of deposited metal microparticles are distributed on the support in the form of islands;
• a measurement step of, after the metal microstructure generation step, measuring an optical response of the metal microstructure generated by the reducing action of the analyte in the metal microstructure generation step on the support;
• and
• an analysis step of, after the measurement step, determining a concentration of the analyte in the measurement solution on the basis of a measurement result of the optical response in the measurement step.