In this paper, we present the design, simulation, and experimental demonstration of a miniaturized low-frequency metamaterial absorber based on the broadside-coupled spiral structures. The tested results indicate that the metamaterial absorber can achieve a miniaturized narrowband absorption with a peak absorption of 98% at 1.39 GHz. Both of the unit cell size and the total thickness of the metamaterial absorber are 6.8 mm that is approximately 1/32 of the working wavelength. Since the spiral structures of the metamaterial absorber are arranged in rotational symmetry, the absorber is polarization-insensitive to the normal incident electromagnetic wave. Additionally, the metamaterial absorber can strongly absorb the obliquely incident electromagnetic wave for both transverse electric and transverse magnetic polarizations, even at 60° angle of incidence.