The invention relates to an automatic device for mixing fluids, particularly paints or varnishes, that are to be sent on to one or more mixing containers (9), said device comprising a plurality of circuits (1), independent of one another, and in particular a circuit (1) for each fluid being dosed, each circuit (1) comprising a storage tank (2) for storage of the fluid, a pump (4) for taking in the fluid from said storage tank (2) and for delivery thereof into said mixing container (9), valves, pipes, and an automatic-control device, also comprised in which are a plurality of precision circuits (1′), each one of which associated in parallel to each of said circuits (1), each of said precision circuits (1′) sharing with the associated circuit (1) the same storage tank (2) and the same automatic-control device and further comprising a precision pump (4′) for taking in the fluid from said storage tank (2) and for delivery thereof into said mixing container (9), as well as valves and pipes of their own.