The present invention relates to an armrest that includes a rotating shaft, an intake port, an exhaust port, an internal duct and a cup holder. The rotating shaft is disposed in the rear end of the armrest body and configured to pivotally connect the armrest body to a seat so that the armrest body may alternate between a retracted position in which the armrest functions as a seatback and an unfolded position in which the armrest functions as an armrest. The intake port, exhaust port, and internal duct are configured to provide heating and cooling of the cup holder.