A protection device (D) of the driving means of a mobile element (O) against the cuttings projection of a machining machine tool comprising a driving section (P1) and a machining zone (P2) of the type that defines a protection wall that, being interdependent from the mobile element (O) that goes through it, separates the driving section (P1) from the machining section (P2). The protection wall is constituted by a plate (100) interdependent from the cross-through part of the mobile element (O) and having a free translational motion on a disk (200) rotating freely with respect to a cabin (300) and the rotation axis (A) of which is shifted with respect to the displacement axis (B) of said mobile element (O). A first displacement window (210) in the disk (200), and a second displacement window (310) in the cabin (300) are provided wherein both displacement windows (210 and 310) are arranged with respect to each other in such a way that the displacement of the mobile element (O) in said second window (310) according to a plane perpendicular to the rotation axis (A) of the disk (200) simultaneously causes the sliding of said plate (100) on the disk (200) and the rotation of the latter, so that said translational displacement of the plate (100) and the rotation of the disk (200) occlude the opening of both displacement windows (210 and 310).