A non-reciprocal circuit element has a metallic component and a resin component combined with the metallic component. Connection electrodes are integrated with the resin component. A permanent magnet is disposed in a region defined by the metallic component. Center electrodes are disposed in a region defined by the resin component and the metallic component. The center electrodes are connected to the connection electrodes with solder (colored gray). The resin component is formed of a white liquid crystalline polymer and the connection electrodes are plated with silver. The connection electrodes and the resin component, therefore, have light reflectances higher than that of the solder. By setting a threshold for binarization between the level of the reflection at the solder and the level of the reflection at the connection electrodes, the amount of applied soldering paste can be determined with an image analyzer.