A safety device (10, 10a) for a portable electric cutting tool (11), of the type comprising a cutting portion (12) with a movable blade (14) that is actuated by way of an electric motor (15) powered by a battery to which it is connected by way of an electric cable (16), the safety device (10, 10a) comprising a shielding layer (18, 18a) made of conducting material with which it covers a body to be protected (17, 17a) from cutting, either the movable blade (14) or the shielding layer (18, 18a) being arranged at a constant and different potential with respect to the other of the two, which is connected to means (20) for detecting the potential and for controlling the movement of the movable blade (14) in order to lock it in the event of variation of the potential of the movable blade (14) or of the shielding layer (18, 18a) at the input of the potential detection and motion control means (20) to which one of the two is connected.
