Device for miniinvasive ultrasound treatment of disc disease. A therapeutic ultrasound tranducer (2) is provided for treatment of the disc (5), of a patient (4) by generating an ultrasonic field (3), of which the temperature focus (F) is located in the disc (5), for heating thereof. The device comprises an optical navigating device (20) with a signal receiving or signal sending unit (32). A reference device (28) has a set position relative to the disc (5). The Therapeutic ultrasound transducer (2) is provided for insertion through the skin of the patient (4) and engagement of the disc (5), preferably anulus fibrosus (8), and it has a flexible wall with an ultrasound transmitting element provided within the flexible wall. Between the flexible wall and the ultrasound transmitting element there is located at least one cooling chamber (11) with cooling liquid for cooling the ultrasound transmitting element and the tissue closest to the therapeutic ultrasound transducer (2) and a temperature sensor is provided to measure the temperature in the disc (5), preferably anulus fibrosus (8).