Provided is a radio wave absorber including: a support; a first radio wave absorption layer having a flat plate shape that is disposed on a surface of the support and includes a radio wave absorption material and a binder; and second radio wave absorption layers that are erected on a surface of the first radio wave absorption layer, include a radio wave absorption material and a binder, and are conical protrusions having bottom surfaces of which outer peripheral portions are in contact with each other, in which a distance between apexes of the conical protrusions adjacent to each other is 0.5 mm to λa mm, in a case where a wavelength of a radio wave to be absorbed is set as λa mm, and a manufacturing method of a radio wave absorber.