In a method for measuring an analyte, which comprises a reaction step of forming a reaction system including a sample containing whole blood, a first substance carried by a solid carrier and specifically binding to an analyte contained in the sample and a second substance specifically binding to the analyte and allowing the analyte to react with the first and second substances and a measurement step of measuring the formed reaction product, (1) the reaction step is performed in a state that blood cells are not disrupted, and (2) at least the reaction step is performed in the presence of a sufficient amount of a detergent that does not cause hemolysis, does not inhibit reactions of the analyte with the first and second substances specifically binding to the analyte and can prevent influence on the reaction system of a component existing in the reaction system.