A microreactor system includes: a microreactor that has two inflow ports into which fluids are introduced and a flow path configured to merge the fluids, and that is configured to mix a first fluid introduced from one of the inflow ports and a second fluid introduced from the other of the inflow ports in the flow path; a first container in which the first fluid is prepared; a second container in which the second fluid is prepared; a first pump configured to feed the first fluid toward the inflow port; a second pump configured to feed the second fluid toward the inflow port; first and second measurement units configured to measure amounts of the first fluid and the second fluid, respectively; and switching units configured to switch at least one of the first fluid and the second fluid to be fed to the microreactor.