Curtain airbag

In order to provide a curtain airbag in that a curtain airbag body is protected by being covered with a cover while a folded and accommodated state within the cover can be directly and visually observed, a curtain airbag (20) includes a curtain airbag body (21) fan-folded to have a long substantially elliptic-cylindrical sectional shape and a cover (22) covering the curtain airbag body (21). On one side surface of the cover (22), openings (26) are formed at predetermined intervals in the longitudinal direction of a folded formation of the curtain airbag body (21), and through the openings (26), the curtain airbag body (21) can be visually observed from outside the cover (22).