A method of manufacturing a circuit-formed substrate is capable of increasing the reliability of an interlayer connection on the circuit-formed substrate, the method comprises the steps of A) limitingresin flow in a hot press process, B) fusing or sticking reinforcement fibers to each other, C) reducing the thickness of substrate material after a filling process, and D) forming a low fluidized-layer with fillers mixed in the substrate material, the material comprising volatile components capable of providing physical properties to control the resin fluidity in the hot press process or efficiently reducing the thickness of the substrate material after the filling process.