A friction stir welding head, intended to be secured to a machine for carrying out friction stir welding using a tool comprising a peripheral shoulder and a central pin, which is surrounded by the peripheral shoulder about a first axis of rotation and which is able to protrude from the peripheral shoulder, the head comprising a frame, intended to be secured to a chassis of the machine, the head comprising a central rotary shaft to which the central pin is intended to be secured, a shoulder securing part, which is located about the central shaft and to which the peripheral shoulder is intended to be secured, the head further comprising a primary rotary shaft for driving in rotation both the shoulder securing part and the central rotary shaft about the first axis of rotation, the central rotary shaft and the shoulder securing part having a coupling device for coupling them to each other, so that the central rotary shaft is integral in rotation with the shoulder securing part about the first axis of rotation and so that the central rotary shaft is free in translation with respect to the shoulder securing part along the first axis of rotation, the head comprising a motor and a second translational drive device for driving in translation the central rotary shaft along the first axis of rotation from the motor during the rotation of the central rotary shaft and of the shoulder securing part about the first axis of rotation, between at least a low position of the central rotary shaft, in which the central pin protrudes from the peripheral shoulder along the first axis of rotation and a high position of the central rotary shaft, in which the central pin does not protrude from the peripheral shoulder along the first axis of rotation, characterized in that the head comprises an external interface part intended to be secured to a rotary spindle of the machine and a first rotation transmission device for transmitting the rotation of the external interface part to the primary rotary shaft about the first axis of rotation, the external interface part projecting from an upper surface of the frame. the head comprising a frame, intended to be secured to a chassis of the machine, the head comprising a central rotary shaft to which the central pin is intended to be secured, a shoulder securing part, which is located about the central shaft and to which the peripheral shoulder is intended to be secured, the head further comprising a primary rotary shaft for driving in rotation both the shoulder securing part and the central rotary shaft about the first axis of rotation, the central rotary shaft and the shoulder securing part having a coupling device for coupling them to each other, so that the central rotary shaft is integral in rotation with the shoulder securing part about the first axis of rotation and so that the central rotary shaft is free in translation with respect to the shoulder securing part along the first axis of rotation, the head comprising a motor and a second translational drive device for driving in translation the central rotary shaft along the first axis of rotation from the motor during the rotation of the central rotary shaft and of the shoulder securing part about the first axis of rotation, between at least a low position of the central rotary shaft, in which the central pin protrudes from the peripheral shoulder along the first axis of rotation and a high position of the central rotary shaft, in which the central pin does not protrude from the peripheral shoulder along the first axis of rotation, characterized in that the head comprises an external interface part intended to be secured to a rotary spindle of the machine and a first rotation transmission device for transmitting the rotation of the external interface part to the primary rotary shaft about the first axis of rotation, the external interface part projecting from an upper surface of the frame.