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We study the relation between chiral and $U_A(1)$ symmetries in thequark-meson model. Although quarks and mesons are described in mean fieldapproximation, the topological susceptibility characterizing the $U_A(1)$breaking comprises two components: one controlled by the condensate and theother by the meson fluctuation. The $U_A(1)$ restoration is governed by thecompetition of these components. In a hot medium, the condensates melt.However, the fluctuation is enhanced. Therefore, the $U_A(1)$ symmetry cannotbe solely restored via the temperature effect. Nevertheless, the baryon densityreduces the condensates and fluctuation, and thereby, the $U_A(1)$ symmetry canonly be restored in a dense or dense and hot medium. The strange condensateplays a weak role in the susceptibility, and the chiral and $U_A(1)$ symmetryrestorations occur almost at the same critical point.

$U_A(1)$ symmetry restoration at high baryon density