A tube connecting apparatus is arranged to hold tubes in a first tube holder and a second tube holder, to rotate a pair of rotatable clamping members which include separable pieces disposed in rotational symmetry for holding the tubes in either or both of the first tube holder and the second tube holder, to heat and melt the tubes by a heated cutting plate moving therebetween to cut the tubes, and to weld cut end faces of the different tubes. When the pair of clamping members are in a state of not holding the tubes rotation preventing members fixedly lock the clamping members in a predetermined position, preventing the clamping member from being rotated.