In the laminated and sintered ceramic circuit board according to the present invention, at least a portion of the inplane conductor is fine-lined, such that the shape of the cross-section surface of the fine-lined inplane conductor is trapezoid, and the height (a), the length (c) of the lower base and the length (d) of the upper base of the trapezoidal cross-section surfaces, and the interval (b) between the lower bases of the trapezoidal cross-section surfaces of the inplane conductors adjacent in a plane parallel to the principal surfaces of the board meet a certain relation. This provides a laminated ceramic circuit hoard with low open failure rate, short-circuit failure rate and high reliability against high temperature and high humidity in a downsized and short-in-height (thin) semiconductor package.