PURPOSE: To uniformly display high heat-transmitting performance by boiling over the length of a heat transmitting tube, by providing the primary cavity part, having the primary openings arranged regularly, in the lower layer, on which the upper layer, consisting of the secondary cavity part, having the secondary openings arranged crosswise in the state of a net, is provided.

CONSTITUTION: In a heat transmitting tube 1 to which the primary cavity part 9 and the primary opening part 10 are provided, the secondary cavity part 15 which is communicated crosswise with each other is formed by depressing the tops of the fins F by some suitable depressing means. The heat transmitting tube 1 is constituted by uniformly laminating the upper layer on the lower layer over the length of a tube, to form a uniform and three-dimensional structure. The lower layer consists of the primary cavity part 9 having the primary opening part 10 in the axial direction of the tube. The upper layer is the secondary cavity part 15, consisting of cavities arranged in the axial and circumferential directions of the tube, having the secondary opening part 14 arranged in the axial and the circumferential directions in the state of a net. In such a structure, a heat transmitting tube of boiling type 1' has a lot of boil producing points for liquid, and part of air bubbles getting off the points are easy to be held in the layers, in addition, feeding of boiling liquid can effectively be performed, passing through the secondary cavity part in the upper layer, as well as the primary cavity part in the lower layer.