To allow to respond to a compricated form, as well as to improve the strength and the rigidity without increasing the weighT an the cost.

In an under bracket 14 of a two wheeler or the like in which a center boss 19 forming a center hole 18, and a pair of fork bosses 21 forming fork holes 20 are connected at a bridge 22, and inner tubes 13 of front tubes can be inserted into the fork holes 20, the under bracket 14 is made of an aluminum cast, the bridge 22 is formed in a hollow box form, and a hollow 34 of the bridge 22 is not opened to the center hole 28, but opened to the fork holes 22, so as to compose the under bracket 14.