To provide an abnormality detecting device for a fuel cell, a fuel cell system and a method for detecting abnormality of the fuel cell system, capable of detecting high possibility of failures in a part of modules of the fuel cell, when an impact is applied.

Fuel cell modules 10 are laminated to form a stack 12, and its both sides are sandwiched by stack supporting plates 14 to form the fuel cell. A first movement sensor 20 to detect the moving condition of the entire fuel cell is attached to the stack supporting plate 14, and a second movement sensor 22 to detect the moving condition of the fuel cell module 10 is attached to the fuel cell module 10 in the vicinity of the stack supporting plate 14. The output of these first and second sensors 20, 22 are inputted in an abnormality detecting part 24, and at a point of time when a difference in the moving conditions exceeds a prescribed threshold value, abnormality caused in the fuel cell is detected.