A flyback converter includes a primary side circuit, a secondary side circuit and a controller. The primary side circuit includes a primary winding and a main switch electrically connected to the primary winding. The secondary side circuit includes a secondary winding and an output diode electrically connected to the secondary winding and having a parasitic electrical parameter. The controller generates a correcting parameter for counteracting an effect on an output voltage of the flyback converter from the parasitic electrical parameter, wherein the parasitic electrical parameter is an equivalent series-connection resistance Rd of the output diode and the secondary side circuit, and the correcting parameter is calculated based on the formula n p n s ⁢ I ini ⁢ R d , wherein np denotes a turns number of the primary winding, ns denotes a turns number of the secondary winding, and Iini denotes an initial current value which is detected when the main switch is conducted.