In the IOT era, development of high-sensitivity micro-magnetic sensors has been progressing. These sensors are classified into two types: Type A, which measures the magnetic resistance or magnetic impedance of the magnetically sensitive part, such as MR sensors and MI sensors; Type B, which measures the coil voltage wrapped around the magnetically sensitive part, such as FG sensors, coil-type MI sensors, and GSR sensors. Type B is used to measure the coil voltage wound around the magnetically sensitive part. The GSR sensor introduced in this chapter is based on a new magnetic sensor principle, the GHz-spin-rotation effect (hereinafter referred to as the GSR effect), and is characterized by the excitation pulse frequency as high as GHz and the magnetic sensitive element which consists of a Co-based amorphous magnetic wire with a diameter of 10 μm and negative magnetostriction and a micro-coil with a coil diameter of 20 μm and a coil pitch of 5 μm, making the element size 1/1 millionth of the FG sensor and 1/100th of the MI sensor. In terms of performance, it has extremely high sensitivity, high signal-to-noise ratio, sine function output, good linearity, and no hysteresis. It is currently under development for applications such as automotive sensors, wearable computers, biomagnetism detection, and in vivo position detection sensors. In this chapter, the GSR principle is introduced, and the current status and future prospects of the development of GSR sensors utilizing the principle are clarified.