PURPOSE: To simplify the fitting structure and save the space by providing cross members at the front and rear between side frames, arranging a reinforcing cross member near one crops member, and installing a fuel tank for an air conditioner in a space section formed between them.

CONSTITUTION: In this electric vehicle installed with a battery device, the right and left side frames 11, 12 are arranged at the lower section of a vehicle body, and cross members 13, 14 are laterally suspended apart from each other at the front and the rear. A reinforcing cross member 15 is laterally suspended between the side frames 11, 12 apart from one cross member 13 by the prescribed size in front of it. A space section 16 is formed between the reinforcing cross member 15 and the cross member 13, and a fuel tank 23 for an air conditioner is inserted and arranged in the space section 16. The space section 16 formed from the reinforcing structure of the vehicle body is utilized, it is advantageous in the viewpoint of space, and the fitting structure of the fuel tank 23 is simplified.