PURPOSE: To provide the reverse osmosis device which is constituted by including plural modules connected in series, produces the permeated liquid having high purity by removing impurities from a raw liquid and particularly makes the modules usable over a long period.

CONSTITUTION: This reverse osmosis device which is constituted by including the plural modules connected in series and produces the permeated liquid having high purity by removing the impurities from the raw liquid is so constituted that the respective ends of the modules 21 to be connected are connected by annular joints which are separately press-fitted from both ends.