A curtain airbag device comprising: a main deploying portion that, at a time when at least one of a small overlap impact or an oblique impact arises, receives a supply of gas and expands, and is deployed in a shape of a curtain along a side window glass; an outer side deploying portion that is formed integrally with a front end side, in a vehicle front-rear direction, of the main deploying portion, and that receives a supply of gas from the main deploying portion and is expanded and deployed; and an inner side deploying portion that is formed integrally with the front end side, in the vehicle front-rear direction, of the main deploying portion, and that receives a supply of gas from the main deploying portion and expands, and is deployed overlappingly at a vehicle width direction inner side with respect to the outer side deploying portion.