If L is a regular language, then the particular L′ is also regular?

Show that if $L ⊆ Σ^∗$ is a regular language then the following language is also regular:

$$L’ = {wmid ∃x, y ∈ Σ^∗ : w = xy ∧ yx ∈ L}$$

Can you give me a hint how to solve that?