Model of magnetic field produced by current lead targeting to 50A is built, and field is calculated utilizing FEA simulation software. Full-bridge topological structure TMR device is designed based on the characteristic which the existence of two points over the lead with the same amplitude and opposite direction of magnetic field. The TMR device was fabricated using the film stack of IrMn/ CoFeB/Ru/CoFeB/MgO/CoFeB/NiFe/Ta. The obtained TMR device possessed the sensitivity of 4.4mV/V/Oe, linear range of 15Gs, and offset of 1% Vcc. The accuracy of the current sensor using this TMR device reached 1%, and the TMR device was proven to be used in current sensor.