A cooking hob with rotary driving means, comprising: a support plate which has a treatment area capable of supporting a cooking vessel provided with rotary blades or paddles connected to an upper magnetic coupling member rotatable about an upper rotating shaft; a lower magnetic coupling member rotatably assembled below the support plate and rotatable about a lower rotating shaft; a drive actuator operatively connected for rotating said lower magnetic coupling member and magnetically transmitting torque to said upper magnetic coupling member of said cooking vessel; and at least one lower magnetic element installed below the support plate at a predetermined distance from said lower rotating shaft of the lower magnetic coupling member to create a magnetic attractive force on an upper magnetic element installed in the cooking vessel at said predetermined distance from said upper rotating shaft of the upper magnetic coupling member when the cooking vessel is located in a predetermined angular position on the treatment area, characterised in that: said lower magnetic coupling member is assembled on a moving support, and a position change actuator is operatively connected to move said moving support between an operative position, in which the lower magnetic coupling member is close enough to the support plate to magnetically transmit said torque to the upper magnetic coupling member when the cooking vessel is located on the treatment area, and an inoperative position, in which the lower magnetic coupling member is far enough from the support plate so as to not transmit the torque; and the lower magnetic element is installed on the moving support to create said magnetic attractive force on the upper magnetic element of the cooking vessel when the moving support is in said operative position. a support plate which has a treatment area capable of supporting a cooking vessel provided with rotary blades or paddles connected to an upper magnetic coupling member rotatable about an upper rotating shaft; a lower magnetic coupling member rotatably assembled below the support plate and rotatable about a lower rotating shaft; a drive actuator operatively connected for rotating said lower magnetic coupling member and magnetically transmitting torque to said upper magnetic coupling member of said cooking vessel; and at least one lower magnetic element installed below the support plate at a predetermined distance from said lower rotating shaft of the lower magnetic coupling member to create a magnetic attractive force on an upper magnetic element installed in the cooking vessel at said predetermined distance from said upper rotating shaft of the upper magnetic coupling member when the cooking vessel is located in a predetermined angular position on the treatment area, characterised in that: said lower magnetic coupling member is assembled on a moving support, and a position change actuator is operatively connected to move said moving support between an operative position, in which the lower magnetic coupling member is close enough to the support plate to magnetically transmit said torque to the upper magnetic coupling member when the cooking vessel is located on the treatment area, and an inoperative position, in which the lower magnetic coupling member is far enough from the support plate so as to not transmit the torque; and the lower magnetic element is installed on the moving support to create said magnetic attractive force on the upper magnetic element of the cooking vessel when the moving support is in said operative position. said lower magnetic coupling member is assembled on a moving support, and a position change actuator is operatively connected to move said moving support between an operative position, in which the lower magnetic coupling member is close enough to the support plate to magnetically transmit said torque to the upper magnetic coupling member when the cooking vessel is located on the treatment area, and an inoperative position, in which the lower magnetic coupling member is far enough from the support plate so as to not transmit the torque; and the lower magnetic element is installed on the moving support to create said magnetic attractive force on the upper magnetic element of the cooking vessel when the moving support is in said operative position.