Let $textsc{k}$＝$F_{q}$(T) be a rational function field. Let $ell$ be a prime number with ($ell$, q-1) ＝ 1. Let K/$textsc{k}$ be an elmentary abelian $ell$-extension which is contained in some cyclotomic function field. In this paper, we study the $ell$-divisibility of ideal class number $h_{K}$ of K by using cyclotomic units.s.s.