A movable mixing device for mixing and/or loosening fodder, which device is provided with a mixing chamber (8) comprising one or more rotors (6) which are rotatable about a vertical axis, which mixing chamber (8) is provided with a bottom (9) and with wall parts (11) which slope upwards toward the outside, and wherein means are present for filling said mixing chamber (8), said means comprising a closable opening in a side wall (11) of said mixing chamber (8), through which the material to be mixed can be supplied to the mixing chamber (8). Said opening is closed by a pivotable moving means being pivotable about an axis near the lower part of the mixing chamber (8).