A microfluidic chip includes a flow passage plate, a flat plate, and an annular seal. In the flow passage plate, a recess forming a flow passage for liquid and a communication hole communicating with the recess are formed. The flat plate is stacked on or under the flow passage plate to close the recess for defining the flow passage. In the flat plate, a communication through-hole communicating with the recess is formed. The annular seal is located on, or formed on, an outer surface of at least one of the flow passage plate and the flat plate, the annular seal surrounding at least one of the communication hole and the communication through-hole. The annular seal is made of an elastomer.