A clutch system selectively transmitting torque in an automatic transmission according to an exemplary embodiment of the present invention may include: a rotation axis rotated by the torque; at least one plate disposed at an exterior of the rotation axis and moved along an axial direction of the rotation axis; at least one disk alternately disposed with the plate and moved along the axial direction of the rotation axis, the disk having at least one wave along a radial direction thereof; and a piston applying force to the disk and the plate along the axial direction of the rotation axis such that a frictional force is generated between the plate and the disk. Therefore, the clutch system of this invention has advantages of enhanced durability and operability.