Disclosed herein is an apparatus for aligning a bill supplied to a transfer path with a center line of the transfer path. The apparatus may include: a first centering roller arranged at one side of the transfer path and applying a frictional force to a portion of the bill positioned at one side of the transfer path so that the bill is moved to the center line, the first centering roller having a first driven wheel formed in a border part to face one edge line of the transfer path; and a second centering roller arranged at the other side of the transfer path and applying a frictional force to another portion of the bill positioned at the other side of the transfer path so that the bill is moved to the center line, the second centering roller having a second driven wheel formed in a border part to face the other edge line of the transfer path.