A method of rounding fin-shaped structures includes the following steps. A substrate including fin-shaped structures, and pad oxide caps and pad nitride caps covering the fin-shaped structures from bottom to top are provided. An isolation structure fills between the fin-shaped structures. A removing process is performed to remove a top part of the isolation structure and expose top parts of the fin-shaped structures. An oxidation process is performed to oxidize sidewalls of the top parts of the fin-shaped structures, thereby forming oxidized parts covering sidewalls of the top parts of the fin-shaped structures. The pad nitride caps are removed. The pad oxide caps and the oxidized parts are removed at the same time, thereby forming rounding fin-shaped structures.