In this paper, we mainly study the function spaces related to H-sober spaces. For an irreducible subset system H and T 0 spaces X and Y , it is proved that Y is H-sober iff the function space C(X, Y ) of all continuous functions f : X −→ Y equipped with the topology of pointwise convergence is H-sober iff the function space C(X, Y ) equipped with the Isbell topology is H-sober. One immediate corollary is that for a T 0 space X, Y is a sober space (resp., d-space, well-filtered space) iff the function space C(X, Y ) equipped with the topology of pointwise convergence is a sober space (resp., d-space, well-filtered space) iff the function space C(X, Y ) equipped with the the Isbell topology is a sober space (resp., d-space, well-filtered space). It is shown that T 0 spaces X and Y , if the function space C(X, Y ) equipped with the compact-open topology is H-sober, then Y is H-sober. The function space C(X, Y ) equipped with the Scott topology is also discussed.