Apparatus and method for detecting a lesion, the method including the steps of applying a voltage to an electrode in contact with a part of a body, sensing signals from an examining part of the body by using probe ( 14 ) having a plurality of sensing electrodes ( 143 ), and calculating a position and a size of a lesion in the body with reference to the signals sensed thus, whereby detecting not only existence of a lesion, but also a position and a size of the lesion.