A character input apparatus which makes it possible to suppress degradation of use-friendliness in a case where a visually disabled user inputs characters using an auto-complete function. In the character string input apparatus, a character string to be input as a portion following a character string input by a user is predicted based on the character string input by the user, and the character string input by the user is completed using the predicted character string as a portion complementary thereto. In a voice guidance mode, information associated with a key selected by the user is read aloud by voice. When the voice guidance mode is enabled, the character string input apparatus disables the auto-complete function and performs control such that a character string cannot be automatically completed.