Swimming goggles include a frame unit, lenses assembled on the frame unit, and a strap unit. The strap unit comprises at least a head strap with at least a free end, and a buckle for securing and adjusting the head strap. The free end defines a plurality of stop grooves therein. The buckle includes a base and a press portion movable radially relative to the base. The base has a first axis and a second axis respectively formed on opposing ends thereof for supporting the head straps. A first abut portion and a second abut portion are formed on the base. The press portion comprises a first stop portion and a second stop portion, an operating portion between the first stop portion and the second stop portion, and a first branch and a second branch respectively on opposite sides of the operating portion.