A grinding device for containers dispensing food products, which includes means for selectively adjusting the distance between blades and teeth and thereby selecting at will the desired grain size for grinding. The device has a static piece that is coupled to the neck of the container and is connected to a rotary piece such that the fixed piece includes a series of teeth which, together with blades projecting from the bottom face of the rotary piece, constitute the grinding mechanism of the device. The device includes, on the outside of the fixed piece, two or more channels that guide the rotation and axial retention of the rotary piece, while the rotary piece contains projections for fitting into the channels of the fixed piece.