pipe 53 coolant supply pipe 54 coolant discharge pipe 59 and hydrogen supply pipe 60 pass through the front wall 23 and rear wall 24 of the fuel cell system box 5 in the aforementioned manner and these are supported in the front wall 23 and rear wall 24 of the fuel cell system box 5 via brackets 66 fixed in place by bolts 65 the front wall 23 and rear wall 24 are both consisted of iron material which has greater weight per unit volume and better support rigidity compared to the aluminum material that forms both side walls 25 and 25 and the bottom wall 26 or the members other than these moreover the front wall 23 and rear wall 24 are provided with a cationic electrodeposition coating and are joined and fixed in the state by rivets 67 to both side walls 25 the bottom wall 26 or other members when the front wall 23 is shown as a specific example in fig6 the front wall 23 is provided with the upper edge flange 23 a the side edge flange 23 b and lower flange 23 c which respectively extend toward the interior the lower edge flange 23 c is overlaid from above by the bottom wall the side edge flange.