Provided is a curtain air bag device including a cushion body provided with a main cushion part and a cushion moving part that is inflated by gas injected from an inflator when the cushion body is deployed and presses the main cushion part in a desired direction, a strap part configured to bind the cushion body such that the main cushion part and the cushion moving part keep a folded shape and to be broken when the cushion body is deployed, and a mounting part connected to the cushion body and coupled to a vehicle body.