Described herein are a spoiler for vehicles and a method of manufacturing the spoiler. The spoiler has a first surface and a second surface which define an appearance of the spoiler, and a hollow part defined in the spoiler. The spoiler includes a reinforcing member which is formed integrally with the second surface and has a frame defining an appearance of the reinforcing member and holes formed in the reinforcing member, and a support unit which is secured to cover the holes of the reinforcing member and an outer surface of the frame, thus supporting the reinforcing member to the second surface. The reinforcing member is formed integrally with the second surface through blow molding.