Abstract: Disclosed is an air liquefaction separation method and apparatus by which the apparatus cost can be reduced when liquid products are collected, the method including: a feed air compression step in which the whole amount of a feed air is a pressurized feed air having a first set pressure which is higher than the operating pressure of the intermediate pressure column; an adsorption and purification step in which impurities are adsorbed and removed from the pressurized feed air to obtain a pressurized purified air; a combining step for a circulating air in which the pressurized purified air and the below-described pressurized returned air are combined to obtain a circulating air; a cooling step in which a first branch air stream of the two divided circulating air is cooled at a first set temperature to obtain an air to be introduced into the intermediate pressure column, and a second branch air stream is cooled at a second set temperature which is higher than the first set temperature to obtain an air for exp