A manufacturing method of a reactor includes: assembling an assembly constituted by a coil and a bobbin by inserting the bobbin, which includes a tube portion and a flange portion, through the coil so that a tip of the tube portion protrudes from the coil; forming a cavity by installing the assembly in a first die so that a portion of a coil lateral face comes into contact with a cavity face of the first die, and closing a second die so that the second die is opposed to the first die; and extending first press rods from a cavity face of the second die toward the bobbin in the cavity, and injecting a resin into the cavity while pressing both ends of the bobbin in an axial direction of the coil from an opposite side to the portion of the coil lateral face.