Multilayer substrate and electronic device

A multilayer substrate (101), in which a plurality of flexible insulating base materials are layered, has a first area (F1) and a second area (F2). The number of layers of the insulating base materials in the second area (F2) is smaller than that in the first area (F1). The multilayer substrate (101) is provided with: a coil antenna (AN) formed in the first area (F1); a magnetic member (4) disposed in the first area (F1); mounted components (1, 2, 3) disposed in the first area (F1); wiring patterns (21, 22, 23, 24); and external connection terminals (E11, E12, E13, E14). The mounted components (1, 2, 3) overlap the magnetic member (4) in their entirety when viewed in the thickness direction (Z direction) and are disposed on the reverse side of the magnetic member (4) from the coil antenna (AN) in the thickness direction (Z direction). At least a part of the coil antenna (AN) overlaps the magnetic member (4) when viewed in the thickness direction (Z direction).