Abstract: A waterproof flashlight includes a cylindrical housing 1, a rotatable annular switch 10, a cylindrical cap 2, an anti-leak gasket 3, a light reflecting member 12, a lens 4, plural light emitting diodes 13 and a position ring 5. The anti-leak gasket, the lens and the position ring are positioned in the cylindrical cap, and the rotatable annular switch is threadably combined with a lower end section of the cylindrical housing. When the rotatable switch is rotated tightly relative to the cylindrical housing, the diodes are turned on to emit light beam, reflected by the light-reflecting member to shoot through the lens. The anti-leak gasket can prevent water from flowing or seeping in the interior of the flashlight.