Disclosed are an apparatus and method for detecting double-feed of paper to prevent banking accidents or jam in a paper handling machine for handling paper, sheets of currency note are not separated by a sheet separating means and thus plural sheets are double fed. The apparatus includes paper feeding means for guiding upper and lower surfaces of the paper and feeding the paper, a pivot member pivotally installed to a rotary shaft, and having a contact portion disposed in a paper feeding path of the paper feeding means and contacting with one surface of the feeding paper, and an encoder portion with a plurality of slits, in which the rotary shaft is closer to the contact portion rather than the encoder portion, and a sensor for counting the number of slits of the encoder portion when the pivot member pivots. The present invention can accurately detect the overlay of the paper having a thin thickness with a simple construction. Also, the present invention can detect the overlay of the paper, regardless of a size and thickness of the paper and a transferring direction of the paper.