A waterproof casing includes a first casing having a first base wall and a first surrounding wall, and a second casing having a second base wall and a second surrounding wall. The first surrounding wall surrounds a periphery of the first base wall to cooperatively define a first receiving recess therewith, and has a first wall surface confronting the first receiving recess, and a first groove provided in the first wall surface. The second surrounding wall is connected to the second base wall proximate to the first surrounding wall to cooperatively define a second receiving recess therewith, and has a second wall surface outwardly of the second receiving recess, and a second groove provided in the second wall surface and corresponding to the first groove. A resilient member is fitted between and closes the first and second grooves. The first and second receiving recesses cooperatively receive a flat panel display.