An eddy-current flaw detection device comprises a magnetic element group of which a specified number of magnetic elements are evenly spaced in each of at least two rows around the surface of a column shaped casing that can be inserted into a conductive pipe, with one row being located at a different position from the other row by ½ the even spacing in the row direction, and switching circuits for switching the magnetic elements in the respective row at time-division. The elements of one row function as magnetic field excitation elements, the elements of the other row function as magnetic field detection elements, and the eddy-current flaw detection device performs eddy-current flaw detection of the conductive pipe by detecting magnetic field excited by magnetic field excitation element by two magnetic field detection elements located at different positions from the magnetic field excitation elements by 3/2 the even spacing.