Abstract: A lamp device for underwater use comprises a sealed beam lamp (1, 3, 5) mounted in a casing (7) designed as a pressure vessel, so that the lens part (1) of the sealed beam lamp constitutes part of the pressure vessel wall in the form of a pressure vessel lid and so that the back side (5) of the sealed beam lamp having the electrical connecting means of the sealed beam lamp is within a water-tight pressure chamber. The pressure vessel casing bears against the back side of the circumferential flange (3) of the sealed beam lamp, a ring sealing means (23) placed in a groove in the casing being arranged therebetween. The flange (3) is applied against the casing (7) by means of a ring plate (19) bearing against the front side of the flange via a pressure balancing packing (27), the ring plate being releasably tightened to the casing.