This paper presents a high-resolution magnetic measurement for detecting vulnerable and suspicious areas on cryptography LSI chips. A CMOS 3-stage low-noise amplifier is integrated with a 500-μm×100-μm magnetic pick-up coil to amplify the induced voltage of the coil. Moreover, the Si-substrate area underneath the coil is removed by applying a Focused-Ion-Beam technique to enhance the coil's performance. High resolution magnetic scanning measurements in a shielded box are performed on both a micro-strip line and a cryptography LSI. By making a comparison with a commercial probe, this measurement holds the advantage that higher-resolution magnetic maps in multiple frequency bands and more revealed information can be achieved.