The tube connecting apparatus of the present invention is arranged as to hold tubes 7, 8 in a first tube holder 1 and a second tube holder 2, to rotate a pair of rotatable clamping members 31, 32 which include separable pieces disposed in rotational symmetry for holding the tubes 7, 8 in either or both of the first tube holder 1 and the second tube holder 2, to heat and melt the tubes 7, 8 by a heated cutting plate 6 moving therebetween to cut the tubes, and to weld cut end faces of the different tubes 7, 8. When the pair of clamping members 31, 32 are in a state of not holding the tubes 7, 8, rotation preventing members 65, 66, 67/71, 72 fixedly locking the clamping members 31, 32 in a predetermined position, preventing the clamping member 31, 32 from being rotated.
