We measured ac loss in Roebel cables consisting of six REBCO strands and ten REBCO strands. The amplitude of the ac transport current and the applied ac magnetic field, and the angle of the applied ac magnetic field to the wide face of the Roebel cable were varied. Measured ac losses of the Roebel cables were compared with those of reference stacks of coated conductors to discuss on the influence of the strand number and the three-dimensional structure of the Roebel cables on their ac loss characteristics.