<p>A tube (10) for a heat exchanger disposed so that an air flow can pass its outer periphery in the lateral direction. The internal inner flow passage (13) is divided into an upstream side flow passage (13a) disposed on the upstream side of the air flow and a downstream side flow passage (13b) disposed on the downstream side of the air flow by a partition wall (14). The partition wall (14) is formed at a position where the width (W1) of the upstream side flow passage (13a) is larger and the width (W2) of the downstream side flow passage (13b) is smaller.</p>
