PURPOSE: A nondestructive inspection device and a method thereof are provided to enable the precise detection of defects and costs reduction by freely moving a magnetic field generator or a magnetic sensor unit. CONSTITUTION: A nondestructive inspection device (10) includes a magnetic field generator (100), a magnetic sensor, a signal processor (400), and a signal display (500). The magnetic field generator is arranged on the top of a target object (CV) and applies a magnetic field to the target object. The magnetic sensor is arranged between the magnetic field generator and the target object, thereby detecting the residual magnetic field of the target object. The signal processor converts the magnetic signals detected by the magnetic sensor into digital signals. The signal display displays or outputs the converted digital signals. The magnetic field generator includes a core member integrating the magnetic field.