An incorrect operation safety lock device for a sliding door or window, said sliding door or window being composed of at least one sash which is movable at least horizontally both ways, along a direction of movement, relative to a fixed frame between a closed position and an open position of the door or window, one handle associated with the movable sash, the handle being operatively connected in at least one point to at least one rod on the upright itself, a control fin protruding from the handle in such a way as to transmit the control movement of the handle to the at least one rod segment, the handle having a handgrip which can be turned about an axis transversal to the direction of movement of the sash; the at least one rod having closing means which act in conjunction with striker elements located on the vertical upright of the fixed frame through sliding of the rod along the upright of the sash when the handle is operated, said safety lock device comprising: - an intermediate block operatively connectable to said rod at the point of connection between the rod and the handle; - a contact element slidably connected to the intermediate block and projecting, in use, outwards from the front of the vertical upright of the sash when the sash is in open position; the contact element comprising a pin which is positioned with its axis (21 X) perpendicular, in use, to the axis of rotation of the handgrip; the contact element having a contact head which, in use, abuts against a vertical upright of the fixed frame when the sash is in the closed position, so as to allow the contact element to withdraw towards the intermediate block; - an elastic member interposed between the contact element and the intermediate block for keeping the contact element in a position where it protrudes from the intermediate block when the sash is in the open position; - a counter plate, disposable internal of the vertical upright of the sash, for fastening the handle to the sash; - a plate for locking the rod, housed in the intermediate block, associated with the contact element and movable with the selfsame element, along its axis, and disposed in a plane perpendicular to said axis of the contact element, from a first operating position for locking the rod, where the plate is received in a recess formed in the counter plate, and a second operating position for sliding the rod, where the plate is away from the recess in the counter plate and which corresponds to the sash closed position; the plate being positioned such that the fin is, in use, interposed between the plate and the working height of the at least one rod. - an intermediate block operatively connectable to said rod at the point of connection between the rod and the handle; - a contact element slidably connected to the intermediate block and projecting, in use, outwards from the front of the vertical upright of the sash when the sash is in open position; the contact element comprising a pin which is positioned with its axis (21 X) perpendicular, in use, to the axis of rotation of the handgrip; the contact element having a contact head which, in use, abuts against a vertical upright of the fixed frame when the sash is in the closed position, so as to allow the contact element to withdraw towards the intermediate block; - an elastic member interposed between the contact element and the intermediate block for keeping the contact element in a position where it protrudes from the intermediate block when the sash is in the open position; - a counter plate, disposable internal of the vertical upright of the sash, for fastening the handle to the sash; - a plate for locking the rod, housed in the intermediate block, associated with the contact element and movable with the selfsame element, along its axis, and disposed in a plane perpendicular to said axis of the contact element, from a first operating position for locking the rod, where the plate is received in a recess formed in the counter plate, and a second operating position for sliding the rod, where the plate is away from the recess in the counter plate and which corresponds to the sash closed position; the plate being positioned such that the fin is, in use, interposed between the plate and the working height of the at least one rod.