A circuit board structure and a fabrication method of the same are disclosed according to the present invention. The circuit board structure includes: a carrier board with at least one surface formed with a circuit layer having electrically connecting pads; a first solder mask formed on the carrier board and the circuit layer and formed with first openings for exposing the electrically connecting pads; and a second solder mask formed on the first solder mask and formed with second openings for exposing the first openings and the electrically connecting pads. The first solder mask is made of a high-insulation photosensitive material characterized by presence or absence of impurities, such as microparticles, to have enhanced fluidity for being filled in the circuit layer, thereby preventing metal ions migration and subsequent metal hypha electricity discharge which might otherwise affect electrical performance, therefore the present invention is applicable to fine circuit fabrication.