Provided is a method for manufacturing a modular inductor device. The method comprises: (a) forming a substrate by using plastic injection, wherein the substrate comprises at least one recessed accommodating groove; (b) placing an iron core in the accommodating groove; (c) arranging two wired circuit layers on the top side of the substrate and two wired circuit layers on the bottom side of the substrate, and performing stitching, hole drilling, electroplating in the holes, and line etching in order to form an internal line and an external line; and (d) performing soldering prevention and junction processing on the external line in order to protect the external line and form a protection layer on the junction so as to obtain the modular inductor device. The substrate is formed by using a plastic injection manner and the iron core is directly placed in the accommodating groove of the substrate, and then subsequent processing programs are carried out. Thus, manufacture programs are greatly simplified, manufacture cost is reduced, and yield rate of final products is increased.