A centrifugal field-flow fractionation device comprising: a rotor having an annular shape and configured to rotate about a rotation axis; a channel member having an arc shape, provided along an inner peripheral surface of the rotor, having an outer peripheral surface having an arc shape and formed on a side of the rotor, and an inner peripheral surface having an arc shape and formed on a side of the rotation axis, including a channel for a liquid sample, and having an inlet in which the liquid sample flows into the channel, and an outlet in which the liquid sample flows out from the channel; a fixing member having an arc shape and provided along the inner peripheral surface of the channel member on the side of the rotation axis with respect to the channel member; a wedge-shaped member attached between opposite ends of the fixing member and configured to apply a force in a direction of spreading the opposite ends apart, so that the fixing member is pressed toward the inner peripheral surface of the rotor; and a rotary actuator configured to rotate the rotor to classify particles in a liquid sample in the channel by centrifugal force, wherein the wedge-shaped member has a pair of contact surfaces that come into contact with the opposite ends of the fixing member, characterised in that: the pair of contact surfaces include tapered surfaces that gradually taper down toward the rotor, so that a distance between the contact surfaces gradually shortens as the contact surfaces come close to the rotor. a rotor having an annular shape and configured to rotate about a rotation axis; a channel member having an arc shape, provided along an inner peripheral surface of the rotor, having an outer peripheral surface having an arc shape and formed on a side of the rotor, and an inner peripheral surface having an arc shape and formed on a side of the rotation axis, including a channel for a liquid sample, and having an inlet in which the liquid sample flows into the channel, and an outlet in which the liquid sample flows out from the channel; having an arc shape, provided along an inner peripheral surface of the rotor, having an outer peripheral surface having an arc shape and formed on a side of the rotor, and an inner peripheral surface having an arc shape and formed on a side of the rotation axis, including a channel for a liquid sample, and having an inlet in which the liquid sample flows into the channel, and an outlet in which the liquid sample flows out from the channel; a fixing member having an arc shape and provided along the inner peripheral surface of the channel member on the side of the rotation axis with respect to the channel member; a wedge-shaped member attached between opposite ends of the fixing member and configured to apply a force in a direction of spreading the opposite ends apart, so that the fixing member is pressed toward the inner peripheral surface of the rotor; and a rotary actuator configured to rotate the rotor to classify particles in a liquid sample in the channel by centrifugal force, wherein the wedge-shaped member has a pair of contact surfaces that come into contact with the opposite ends of the fixing member, characterised in that: the pair of contact surfaces include tapered surfaces that gradually taper down toward the rotor, so that a distance between the contact surfaces gradually shortens as the contact surfaces come close to the rotor.