We investigated the magnetic domain structures of nickel rhomboid lattice antidot arrays. The change in the magnetic anisotropy due to the geometrical effect of the lattice was investigated by measuring the normalized longitudinal Kerr rotation hysteresis curves. When the external magnetic field direction inclined to the nearest-neighbor hole direction at angles of 30 degrees, 90 degrees, and 150 degrees, an easy axis exhibited a more square loop with increase in coercivity. In addition, a magnetic easy axis like domain configuration was obtained. This result can be explained by an enhanced geometrical effect with shape anisotropy. From these results, the field-dependent change of the magnetic domain structures can be ascribed to the shape anisotropy induced by the ferromagnetic antidot array. (C) 2011 Elsevier B.V. All rights reserved.