A substrate structure is provided with a first electrical contact pad formed on an insulating layer of a substrate body, where the first electrical contact pad includes a first pad portion disposed on the insulating layer and at least one first protruding portion embedded in the insulating layer, so that the first pad portion is electrically connected to a circuit layer in the insulating layer by a conductive blind via, and the first protruding portion is free from being electrically connected to the circuit layer, such that, through a design of the first protruding portion, all surfaces of a metal layer formed on the insulating layer can meet the requirement of coplanarity.