Target substance separation method and quantification method

A method for measuring a target substance amount, the method comprising:

• forming a mixture containing:
• a target substance-magnetic particle-labeled substance complex that comprises:
• a biological sample containing a target substance, and
• magnetic particles to which a first receptor is fixed, wherein the first receptor is adapted to specifically recognize a site of the target substance, and
• a labeled substance to which a second receptor is fixed, wherein the second receptor is adapted to specifically recognize a site different from the site of the target substance;
• separating the target substance-magnetic particle-labeled substance complex from the mixture by magnetism and electrophoresis;
• and
• a subsequently, measuring the target substance amount in the biological sample, which comprises detecting a signal intensity of the target substance-magnetic particle-labeled substance complex.