In a method of testing an electrode structure in which a plurality of electrodes are arranged in a matrix, a test unit is positioned at a position of a target one of the plurality of electrodes apart from the target electrode by a preset distance. The test unit has a MISFET having a source, a gate and a drain. Then, a first voltage is applied to the target electrode such that a gate voltage is induced at the gate by electrostatic induction. Also, a second voltage is applied to at least one of the source and the drain such that current flows between the source and the drain based on the gate voltage. Then, a value of the current is examined to determine an electrical connection state of the target electrode.