A method of manufacturing a ceramic substrate includes the steps of preparing a ceramic paste in which a powder of at least one of a metal boride and a metal silicide is added to a raw material powder of a glass ceramic, applying the ceramic paste to a green sheet which is to become a ceramic layer after firing, applying a conductor paste which is to become a conductor trace after firing to the ceramic paste having been applied to the green sheet, and firing the green sheet carrying the ceramic paste and the conductor paste applied thereto.