PROBLEM TO BE SOLVED: To provide a technique that does not cause leakage of small fluid even by a small dimensional distortion, and yet eliminates the need for a large force in the removal of a stopper, while the stopper attached to a fluid port in the case comes into close contact with a port inner surface, in a module used for medical care, water treatment or food products.SOLUTION: A module has a case having a cylindrical fluid port and a stopper attached to the fluid port. The module is characterized as follows: the stopper is configured such that annular sealing parts of two places or more and four places or less are projected from a cylindrical part and the side face of the cylindrical part, and are inserted inside the fluid port the fluid port has recessed sections of 10 &mum or more and 100 &mum or less existing in an inner surface and at least one of the sealing parts is disposed at the position avoiding the recessed sections so as to come into abutment therewith.
