Disclosed herein are a method and apparatus for measuring flow using an electromagnetic resonance phenomenon. The flowmeter includes an RF resonator in the form of a cylinder into which a transmission antenna for forming a magnetic field in a preset frequency range and a reception antenna for measuring a response signal are inserted, the RF resonator being shielded from an external magnetic field; and a processor for measuring the flow in a pipe that passes through the RF resonator based on the response signal. The RF resonator includes circular holes in the two bases of the cylinder so as to enable the pipe to pass through the RF resonator, and is formed with a first body and a second body, which are split in the height direction of the cylinder and are coupled using a coupling member so as to wrap the outer circumferential surface of the pipe.