PURPOSE: To provide a key input circuit which is capable of preventing the circulation of a signal caused by the simultaneous pressure of plural key switches and is small-sized and inexpensive.

CONSTITUTION: A key input array KA is composed by arranging plural key switches SW1 to SW9 in a matrix state. On each column line CL 1 to CL 3 of the key input array KA, power source voltage Vcc is impressed via pull-up resistors R1 to R3. In each row line RL 1 to RL 3 of the key input array KA, low active strobe signals STB 1 to STB 3 are imparted. Further, on each row line RL1 to RL3, diodes D1 to D3 are provided. By these diodes D1 to D3, the of a signal is prevented.