Ion exchanger (1) used in a cooling
system (50) of a fuel
cell system, comprising: a connecting
pipe portion (2) having both end portions configured to be respectively connectable to a predetermined
pipe of the cooling
system, the connecting
pipe portion having a first flow path (R1) allowing a
coolant introduced from one side to flow therethrough to the other side; a housing portion (3) intended to communicate with the connecting pipe portion; and a storage body (4, 5) mounted on the housing portion, having a second flow path (R2) in which a part of the
coolant introduced into the connecting pipe portion branches and flows out of the connecting pipe portion and flows into the connecting pipe portion again, and stores an
ion exchange resin (18) in the second flow path, wherein: an installation state of the storage body (4, 5) with respect to the housing area (3) can be changed in a variety of ways; and a proportion of the
coolant in the connecting pipe region (2) flowing to the second flow path (R2) can be changed by changing the installation state of the storage body (4, 5), in which the storage body has a part mounted to project to the inside of the connecting pipe portion (2), and an
inlet channel through which the coolant from the connecting pipe portion is introduced into the second flow path (R2) at the projecting part, and an outlet channel through which the coolant from the second flow path is discharged to the connecting pipe portion, and the installation state of the storage body (4, 5) can be changed by rotating the storage body by a predetermined angle with respect to an installation direction of the storage body with respect to the housing area (3) as an axial center, further comprising a movable piece (25), one end of which is pivotally mounted so that it is rotatable, and the other end of which is a free end on the connecting pipe area-side end face (10) of the storage body (4, 5) which projects to the inside of the connecting pipe area (2), in which a free end side of the movable piece (25) changes between a state in which it is positioned further on the upstream side of the first flow path (R1) than a rotation axis side and a state in which it is positioned further on the downstream side of the first flow path than the rotation axis side by changing the installation state of the storage body (4, 5).