Let $L^{2}=L^{2}(D,rdrd\theta/\pi)$ be the Lebesgue space on the open unit disc $D$ and let $L_{a}^2=L^{2}\cap\mathrm{Hol}(D)$ be a Bergman space on $D$. In this paper, we are interested in a closed subspace $\mathcal{M}$ of $L^{2}$ which is invariant under the multiplication by the coordinate function $z$, and a Hankel-type operator from $L_{a}^2$ to $\mathcal{M}^\bot$. In particular, we study an invariant subspace $\mathcal{M}$ such that there does not exist a finite-rank Hankel-type operator except a zero operator.