A nozzle unit for applying damping material onto a work piece, comprising: a nozzle that has a discharge port, which has a slit shape, and that discharges the damping material from the discharge port; a motor that is fixed to the nozzle; and a slit width changing device that changes a slit width of the discharge port using rotation of the motor, characterized in that it further comprises a gear box, wherein: the motor is arranged in such an orientation that a first rotary shaft of the motor is aligned in a direction in which the damping material is discharged from the nozzle; the gear box transmits rotation of the first rotary shaft to a second rotary shaft that extends toward the nozzle; the slit width changing device changes the slit width of the discharge port in accordance with rotation of the second rotary shaft; the second rotary shaft extends from the gear box toward the nozzle and is formed of a first shaft, a second shaft and a connecting member, the first shaft is connected to the gear box; and the second shaft is connected to the first shaft via the connecting member so that the second shaft is slidable in the axial direction with respect to the first shaft and the second shaft is not rotatable with respect to the first shaft. a nozzle that has a discharge port, which has a slit shape, and that discharges the damping material from the discharge port; a motor that is fixed to the nozzle; and a slit width changing device that changes a slit width of the discharge port using rotation of the motor, characterized in that it further comprises a gear box, wherein: the motor is arranged in such an orientation that a first rotary shaft of the motor is aligned in a direction in which the damping material is discharged from the nozzle; the gear box transmits rotation of the first rotary shaft to a second rotary shaft that extends toward the nozzle; the slit width changing device changes the slit width of the discharge port in accordance with rotation of the second rotary shaft; the second rotary shaft extends from the gear box toward the nozzle and is formed of a first shaft, a second shaft and a connecting member, the first shaft is connected to the gear box; and the second shaft is connected to the first shaft via the connecting member so that the second shaft is slidable in the axial direction with respect to the first shaft and the second shaft is not rotatable with respect to the first shaft. the motor is arranged in such an orientation that a first rotary shaft of the motor is aligned in a direction in which the damping material is discharged from the nozzle; the gear box transmits rotation of the first rotary shaft to a second rotary shaft that extends toward the nozzle; the slit width changing device changes the slit width of the discharge port in accordance with rotation of the second rotary shaft; the second rotary shaft extends from the gear box toward the nozzle and is formed of a first shaft, a second shaft and a connecting member, the first shaft is connected to the gear box; and the second shaft is connected to the first shaft via the connecting member so that the second shaft is slidable in the axial direction with respect to the first shaft and the second shaft is not rotatable with respect to the first shaft.