A radio wave absorber provided with a radio wave absorbing film formed on a substrate, the radio wave absorber being capable of absorbing radio waves over a broad frequency band and exhibiting superior radio wave absorbing properties even with a radio wave absorbing film thinner than 1 mm. A film forming paste suitable for forming a radio wave absorbing film that is provided in the radio wave absorber. In a radio wave absorber provided with a radio wave absorbing film formed on a substrate, a particular epsilon-type iron oxide is employed in the radio wave absorbing film and relative permittivity of the radio wave absorbing film is set to 6.5 to 65.