A mobile floor device for a swimming pool including a stationary floor, standing lateral walls, a mobile floor and a mechanism for pulling said mobile floor. The pulling mechanism includes cables and drivers driving the cables in one direction or in a reverse direction. Each cable having a first end connected to the mobile floor and a second end connected to the swimming pool. For each cable, at least one driver drives a maximum of one cable. The drivers are attached either to the swimming pool or to the mobile floor with the lengths of the cables between the drivers and the mobile floor and the swimming pool, respectively, being substantially equal to one another.