The ECC circuit includes a Chien search unit configured to determine whether there is an error in each bit of a data sequence. The Chien search unit selects a coefficient of a nonlinear term from among terms of an error locator polynomial as a nonlinear coefficient, separates the error locator polynomial into a first location equation including only linear terms and a second location equation including only nonlinear terms, determines a third location equation by dividing the first location equation by the nonlinear coefficient, determines a fourth location equation by dividing the second location equation by the nonlinear coefficient, and determines whether there is an error for each of the bits by performing an XOR operation on a result of the third location equation using the substitution value and a result of the fourth location equation using an arbitrary element of the error locator polynomial as a substitution value.