In the case when there are two objective biological activities, and the aim is to isolate a compound having at least one biological activity, the present inventors developed an assay method wherein a common detection marker is utilized for separately detecting the presence or absence of each of the biological activities. The present inventors discovered that a compound having at least one of two or more distinct biological activities can be efficiently and conveniently detected by simultaneously assaying at least one test sample or more by the above-mentioned method. Furthermore, for a test sample that proved to be positive by the detection method, they found that it is possible to efficiently and conveniently screen for a test sample having an objective specific biological activity by combining with a method wherein an individual activity of a test sample can be detected to specify the biological activity.