To provide a circuit board which has a thick and fine wiring pattern, a high adhesion strength of the pattern to the board and high reliability and to realize a high output module having a small size and a high performance.

The circuit board comprises first metal layer formed in a pattern on a ceramic board, a second metal layer laminated on the first metal layer and formed in a pattern, and a third metal layer formed to cover the overall surface and the side face of the second metal layer and the part of the first metal layer. In this board, the first metal layer not covered with the third metal layer is narrowed in width by etching.