A vehicle pop-up hood device actuator (110) includes a main body section (120); a cylinder (112) that covers a portion on one axial direction side of the main body section (120), that is moved toward the one axial direction side of the main body section (120) by generated gas to lift a hood of a vehicle to a lifted position; and that is configured so as to be capable of moving to a retention position, a sealing member (126) that is formed in a ring shape and that forms a seal between the main body section (120) and a general face; a retention member (132) that abuts on an inner peripheral face of the cylinder (112) and retains the cylinder (112) at the retention position; and an enlarged diameter face (114A) that is disposed at a radial direction outer side of the main body section (120) with respect to the sealing member (126) at the lifted position.
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