A position detecting device has an output circuit, which controls voltages of signal lines connecting a power supply and a ground by a power side transistor and a ground side transistor. An output signal line connects a connection point of the signal lines and an output terminal. A first comparator circuit outputs a signal “1” when a current flowing in the line between the power supply and the connection point is larger than a normal current flowing into the ground from the power supply in a normal state. A second comparator circuit outputs a signal “1” when a current flowing in the line between the connection point and the ground is larger than the normal current. When the signal “1” is output from the first comparator circuit or the second comparator circuit, a cutoff circuit turns off a switch disposed in the output signal line.