The present invention has an object to enhance the reliability of the electrical connection of a silver-based conductor film on the surface of a glass ceramic board. In order to achieve the object, according to the present invention, by the use of a conductor paste containing a silver particle having a specific surface area of 0.3 m2/g to 3.0 m2/g and no glass, printing is carried out on a glass ceramic board and the conductor paste is fired at a firing temperature having a difference of ±50° C. from a softening temperature of amorphous borosilicate glass contained in the glass ceramic. Consequently, a silver-based conductor film having high reliability of the electrical connection is formed on the ceramic board.