PURPOSE: To mount a microwave circuit with high density by constructing a circuit element without changing the width of a microstrip line.

CONSTITUTION: A dielectric substrate 1 contains a ground layer 2 on one of both sides and a strip line 3 formed on the other side respectively. In such a constitution of a microstrip line, a high dielectric constant layer 4 is laminated in an area including a circuit element area between the substrate 1 and the line 3. So that the dielectric constant is partly increased for the dielectric constant placed between the layer 2 and the line 3. Then the impedance of the dielectric member is varied, and a capacity element is obtained.