PURPOSE: To a reduce the cost by forming a bracket in small size.

CONSTITUTION: In a reserve tank 1, an engaging groove 5 engaged with an end part of a bracket 2 is formed in a tank upper surface la, and a protrusion part 6 fitted to a hole part of a car body side 3 is integrally provided in a tank bottom surface. In the bracket 2, one end side end part is inserted in a press fit condition to the engaging groove 5 along a guide surface of the tank upper surface 1a from sideward the reserve tank 1, and the other end side is fixed to the car body side 3 by a bolt 7. In this way, the reserve tank 1, in a condition that the tank bottom surface is supported on the car body side 3, by holding the tank upper surface 1a pressed downward by the bracket 2, is fixed on the car body side 3.