An electromagnetic shield 1a includes a plate-shaped base 5, a plurality of first projecting portions 32, and a plurality of second projecting portions 2. The plate-shaped base 5 has a first surface 10 and a second surface 20. The first surface 10 is a surface configured to allow an electromagnetic wave Ei to be incident on the first surface 10. The second surface 20 is a surface being distant from the first surface 10 and extending along the first surface 10. The plurality of first projecting portions 32 project from the first surface 10 in a direction away from the second surface 20. The plurality of second projecting portions 33 project from the second surface 20 in a direction away from the first surface 10. The electromagnetic shield 1a includes a dielectric.