Disclosed herein is a curtain airbag cushion. The cushion has a length appropriate for being deployed to the chest of a passenger. A blocking part which partitions the interior of the cushion into portions is oriented in the vertical direction. The lower end of the blocking part is spaced apart from the bottom of the cushion by a predetermined distance. Thus, when an inflator explodes, gas discharged from the inflator is guided towards the lower portion of the cushion and then guided towards the front or upper portion of the cushion through the space between the lower end of the blocking part and the bottom of the cushion.