Provided is a centrifugal field-flow fractionation device that can stably press a fixing member toward an inner peripheral surface of a rotor by a wedge-shaped member, even when a relatively large centrifugal force acts on the wedge-shaped member. An arc-shaped (C-shaped) fixing member 17 is provided along an inner peripheral surface of a channel member 16 on a side of a rotation axis of the channel member 16. A wedge-shaped member 18 is attached between opposite ends of the fixing member 17 and applies a force in a direction of spreading the opposite ends apart, to thereby press the fixing member 17 toward the inner peripheral surface of the rotor 14. The wedge-shaped member 18 has a pair of contact surfaces 184 that respectively come into contact with the opposite ends of the fixing member 17. The pair of contact surfaces 184 include tapered surfaces that gradually taper down toward the rotor 14, so that the distance between the contact surfaces 184 gradually shortens as the contact surfaces 184 come close to the rotor 14.