This paper describes interaction of vortex rings, whose number ranges 3 to 20, travelling along a common axis. A train of rings were produced by using a computer-aided plunger drive, whose apparatus made generation of each vortices controllable in principle. Smoke visualization method was utilized, and the motion of vortices was analyzed. The results were compared with those based on perfect fluid theory. Several specific features of the interactions were clarified; especially, it was found that the merging location of two vortices was jittering in space, and its feature was quite different from that of the theory. Finally, the problems involved in the apparatus were pointed out.