To secure and facilitate the exchange of a liquid supplying pipeline by providing an exchangeable partitioning plate formed with plural pipelines for connecting each pair of pipeline and for switching liquid flow to each column of a continuous ion exchanger device using plural columns.

This joint assembly is formed of a base plate A, a partitioning plate B, a repressing member C, and pipelines from an inlet and an outlet of each column are connected to the base plate A. The base plate A is formed with a pipeline connected to liquid reservoirs for four kinds of liquid to be supplied and connected to four positions as final discharge points. The partitioning plate B is formed by sticking three plate members B1-B3 capable of being separated at f-f1, g-g1. The first plate member B1 is formed with a through-hole facing to an opening provided in a back surface of the base plate A, and the second plate member B, is formed with grooves as flow passages corresponding to the through-holes at both ends thereof in both surfaces, and these plate members are replaced so as to exchange the liquid supplying pipeline.