An input/output controller, including: a first/a second input/output units that sends and receives data to and from a first and a second external apparatus, a third input/output unit operating in one of a plurality of working modes including a first/a second working mode for sending and receiving data to and from the first/the second external apparatus, an abnormal state detecting unit which detects that the first input/output unit or the second input/output unit is in an abnormal state and a working mode setting unit which makes the third input/output unit operate in the first/the second working mode when it is detected that the first/the second input/output unit is in an abnormal state.