Abstract: The present application provides a device for detecting a defect in a steel cord ply. The device is configured to obtain an enhanced magnetic field signal of the steel cord ply and detect a defect of the steel cord ply based on the enhanced magnetic field signal. The device includes a magnetic field unit including a permanent magnet configured to generate a background magnetic field; a signal obtaining unit configured to generate an enhanced magnetic field signal of a steel cord ply based on a plurality of first magnetic field signals and a plurality of second magnetic field signals; and a defect detecting unit configured to detect a defect of the steel cord ply based on the enhanced magnetic field signal, wherein the defect detecting unit includes an AD converting module, a signal processing module, a defect detecting module, a display module, and a control module.