that the beads 14 b 15 b can be formed being overlapped with each other in the case of type 3 the cross sectional shape of the primary portion of the beads 14 c 15 c to be formed is not an arc formed along the tube wall but a linear shape which is made by means of pressing when the above bead type in which the bead shape is changed provides the same operational effect as that of the original type it can be applied concerning the characteristics of various bead patterns of the second to the fifth embodiment relative evaluations of the heat radiating performance and the pressure loss resistance index are shown in fig1 in the case where the heat radiating performance and the pressure loss resistance index of the conventional tube structure having the two dimensional protrusions are set at 100 the experiment was conducted on an egr gas cooler in which the heated gas air is passed through ten tubes and the tubes are cooled by water outside under the following conditions as a result the following can be confirmed when the adjoining beads are shifted from each other in the circumferential direction or the beads are inclined with respect to the circumferential direction the pressure loss can be reduced and the heat radiating performance can be enhanced without deteriorating the heat transfer facilitating effect as described above in the tube structure of the multitubular heat exchanger according to a first aspect of the invention of the present invention the shape and the arranging method of the bead which.