A curtain airbag apparatus for a vehicle, the curtain airbag apparatus including a mounting tab folded in an upward/downward direction so that portions of the mounting tab overlap one another, and having a decreased vertical length in an assembled state, a cushion folded in the assembled state and configured to move downward while inflated when deployed, and a tab strap having one end coupled to the mounting tab and the other end fixed to the mounting tab in a state in which the tab strap surrounds the cushions, in which when the cushion is deployed, a folded portion of the mounting tab is unfolded, such that the mounting tab is extended, and a position of the cushion is moved downward.