Forced composition cycling was conducted for oxidative coupling with Bi(2)O(3)-P(2)O(5) in a microreactor in order to obtain high benzene yield and suppress CO(2) production. A microreactor suitable for controlling flow was thought, to work effectively in conducting forced composition cycling because it restrains axial diffiusion. The results for cyclic operation of the microreactor and a packed bed reactor were compared on the basis of relaxation time. With the microreactor, forced composition cycling in a short period, 12 s, could be carried out. Although the shapes of the response curves for the microreactor (period: 12 s) and the packed bed reactor (period: 72 s) were similar when the periods were normalized, those of product yields were different. This is because the response to composition change was so accurate that the catalyst was kept in a high oxidation state. The maximum value of benzene production by forced composition cycling with the microreactor was about 4 times that of the steady state and about 2 times the maximum value of benzene production by forced composition cycling with the packed bed reactor.