To provide a substance for inhibiting the activation of a G-protein conjugate type receptor, and a method for screening the same.

This G-protein conjugate type receptor inhibitor contains a compound selected from trans type fatty acids as an active ingredient. Also, a medicine containing the G-protein conjugate type receptor inhibitor as the active ingredient can be provided. By adding a compound to be tested such as the trans type fatty acid, etc., to G-protein conjugate type receptor-holding cells, it is possible to perform a screening for detecting a substance showing an adverse effect on a living body or a substance correcting the adverse effect.