To perform straight expansion even when an aspirator installation point is moved to a position capable of evading interference with a machine body and seawater suction at the time of the expansion on the surface of the sea without becoming the obstruction of passengers' escape relating to the emergency escape device of a single air chamber type equipped in an airplane or the like.

A horizontal direction auxiliary air chamber 2 connected to left and right main air chambers 1a and 1b is provided near a folding line 6 to be spread in the initial stage of the expansion and a part on the left side in the figure from the folding line 6 is swollen to a square shape from a plane view by the function of the auxiliary air chamber 2 until the connection of tie-backs 4 and 4-1 and 5 and 5-1 is released. Thus, even when an aspirator 3 is locally arranged, the expansion is performed straight.