An apparatus for converting character mistyping is installed in a computer having a keyboard and a keyboard driver as an input device, and having an operating system for converting a scan code input from the keyboard driver into a character, and for generating a keyboard message in a current window having an input focus. The apparatus consists of: a scan code detector for detecting a scan code when the scan code input through the keyboard is transmitted to a kernel of the operating system via the keyboard driver; a scan code buffer for storing a scan code; a buffer manager for analyzing the scan code detected by the scan code detector, for storing the scan code in the scan code buffer if the analyzed scan code is a character code, and for deleting all scan codes stored in the scan code buffer if the analyzed scan code is not a character code; an event detector for detecting an event indicating a character mistyping conversion; and a character mistyping converter for deleting mistyped characters in the current window having an input focus, and for generating a keyboard message in the current window by character-mistyping-converting the scan code stored in the scan code buffer when an event is detected by the event detector. Thus, the character mistyping conversion can be performed on all application programs or general edition windows running on the operating system without additional code needed for supporting the character mistyping conversion function.