Provided is a technique for achieving a higher measurement accuracy in the detection of an organism-originated physiologically active substance or the measurement of the concentration of the organism-originated physiologically active substance in a hyaluronic acid preparation. The present invention relates to a measurement method for detecting an organism-originated physiologically active substance or measuring the concentration of the organism-originated physiologically active substance in a hyaluronic acid preparation by mixing the hyaluronic acid preparation with an AL reagent to allow the organism-originated physiologically active substance in the hyaluronic acid preparation and an AL to react with each other. A mixed solution of the hyaluronic acid preparation with the AL reagent is diluted with an aqueous electrolyte solution, and a specific protein having a higher affinity for the organism-originated physiologically active substance than that of hyaluronic acid is added to the mixed solution.