It is an object of the present invention to provide a method for simultaneously carrying out the detection or measurement of a substance interacting with a physiologically active substance immobilized on a biosensor and the analysis of the effects of the above substance on the biological activity of the physiologically active substance. The present invention provides a method using a biosensor formed by immobilizing a physiologically active substance on a substrate, wherein the detection and measurement of a substance interacting with said physiologically active substance and the measurement of the biological activity of said physiologically active substance are carried out on said single biosensor.