Key input device and mobile communication terminal using the key input device

A key input device comprising:

• a key matrix circuit including a plurality of key switches and a matrix of row signal lines and column signal lines, a different one of the key switches being provided at each intersection of a row signal line and a column signal line;
• a reception unit configured to receive, from the key matrix circuit, first detection information related to electrical connection between each row signal line and each column signal line;
• a determination unit configured to determine, based on the first detection information, whether a possibility exists that a user has pressed at least three key switches simultaneously and electrical connection between signal lines for a key switch that has not been pressed has been erroneously detected;
• and
• an output control unit configured to output information in accordance with one or more key switches pressed by the user based on the first detection information when the determination unit determines that the possibility exists and to block output based on the first detection information when the determination unit determines that the possibility does not exist.