Swimming goggles include a frame body, lenses, buckles attached to left and right portions of the frame body, and a head strap passed through the buckles. Each of the buckles has a base having a connecting portion and a guiding portion, and an operating portion. With the head strap being frictional engaged with the guiding portions and retained by the operating portion and being stretched after wearing of the swimming goggles, the head strap is adjustable through the buckles without taking off the swimming goggles, so as to provide a quick and easy adjustment, and a lower cost of manufacturing because of simplified structure.