A multilayer substrate includes a stacked body of insulating base material layers and conductor patterns on the insulating base material layers. A thickness adjustment base material layer includes a frame portion, an opening portion inside the frame portion, and an island shaped portion inside the frame portion, and connection portions to connect the island shaped portion to the frame portion. The conductor patterns, in a stacking direction of the insulating base material layers, are wound around the island shaped portion. A line width of the connection portions is smaller than the width of the island shaped portion connected to the frame portion through the connection portions. An area overlapped with the conductor patterns is larger in the opening portion than in the frame portion and the island shaped portion.