Automatic cleaning device (1) for a surface submerged in a liquid, designed to be connected to a pump, includes: a hollow head (2) that has a seat (11), first intake hose (5a) and second intake hose (5b) emptying into said hollow head (2), the seat (11) delimiting a space in which a flap valve (4) is housed, said flap valve (4) being able to work with said seat (11) so as to switch to the first and second blocking positions in which it respectively blocks the first intake hose (5a) and second intake hose (5b) during the operation of said device (1), characterized in that a prefilter (9) is placed in the hollow head (2) so as to keep the flap valve (4) from being clogged in the space.