A manufacturing method of a circuit substrate includes the following steps. A dielectric layer is formed on at least one surface of a substrate. An insulating layer is formed on the dielectric layer. A portion of the insulating layer and a portion of the dielectric layer are removed, so as to form at least one blind via in the dielectric layer and the insulating layer. An electroless plating layer is formed on the sidewall of the blind via and a remaining portion of the insulating layer, wherein the binding strength between the insulating layer and the electroless plating layer is greater than that between the dielectric layer and the electroless plating layer. A patterned conductive layer is plated to cover the electroless plating layer.