To provide a character input detection method for surely detecting user's depression of one key on a terminal device and user's simultaneous depression of two keys in the terminal device.

The terminal device writes the depression time of a first key in t1 of a storage part (steps S01 to S04), and at the time of detecting the depression of a second key within prescribed time td after the t1, writes the time in t2 of the storage part (steps S05, S06, S08, S09) and obtains a character or a symbol corresponding to the combination of the first and second keys (steps S10 to S17). When the character or the symbol corresponding to the combination of the first and second keys does not exist, the terminal device obtains a character or a symbol corresponding to the first key, retreats the information of the second key and waits for succeeding user's operation (steps S18, S19). When the second key is not depressed after the depression of the first key, the terminal device obtains the character or the symbol corresponding to the first key (steps S06, S07).