To provide a technology relating to an electric power conversion system which supports a lamination cooling unit with an elastic member and inhibiting variations in lengths of the elastic members due to variations in lengths of the lamination cooling units.

An electric power conversion system includes: a lamination cooling unit 2; a base plate 10 for attaching the lamination cooling unit; a spring 21 biasing the lamination cooling unit 2 between stopper parts 12, 13 of the base plate 10; and spacers 22, each of which is inserted between the stopper part 13 and the spring 21. Protruding parts, having different protruding lengths, are respectively provided on both surfaces of the spacer 22. Case side recessed parts 13a, each of which is a recessed part fitted with the protruding part and has a depth that is equal to or smaller than the maximum length of the spacer side protruding part and is equal to or larger than the minimum length of the spacer side protruding part, are respectively provided on spacer contact surfaces of the stopper parts 13.