An apparatus for preventing corrosion of a contact includes a detection conducting path connected to the contact, a variable impedance unit and a comparing and switching unit. The variable impedance unit is connected to the detection conducting path. The variable impedance unit is switchable between (i) a first impedance used for passing a corrosion prevention current into the detection conducting path and (ii) a second impedance through used for passing a current, which is used for detecting a connection state of the contact, into the detection conducting path. The first impedance is lower than the second impedance. The comparing and switching unit compares a detected value with a corrosion threshold, compares the detected value with a restoration threshold and switches the variable impedance unit based on comparing results.