A vapor-liquid separator includes an outer tube, an introduction tube, a delivery tube, and a discharge tube. The introduction tube allows passage of a vapor-liquid two-phase fluid in a swirling state. The delivery tube allows passage of the vapor phase separated from the vapor-liquid two-phase fluid. The introduction tube and the delivery tube are coaxially provided at the corresponding axially opposite ends of the outer tube. The discharge tube is provided on the outer tube in the vicinity of the axial end face of the outer tube on the side toward the introduction tube. The discharge tube is adapted to discharge therefrom the liquid phase separated from the vapor-liquid two-phase fluid. An outlet of the introduction tube and a delivery port of the delivery tube are located axially inside the outer tube by respectively predetermined axial distances while facing each other with a predetermined axial distance therebetween.