A composite circuit substrate structure includes a first dielectric layer, a second dielectric layer, a glass fiber structure, and a patterned circuit. The first dielectric layer has a first surface and a second surface opposite to each other. The second dielectric layer is disposed on the first dielectric layer and entirely connected to the first surface. The glass fiber structure is distributed in the second dielectric layer. The patterned circuit is embedded in the first dielectric layer from the second surface, and the patterned circuit is not contacted with the glass fiber structure.