Two types of Rotman lenses have been designed to show the feasibility of multi-layer Rotman lenses for millimetre-wave system-in-package applications. Firstly, a two-layer Rotman lens-fed antenna array is designed to reduce the total size of the beamforming antenna array. A new design of constrained lines is proposed to reduce the delay lines. In addition to the size reduction, the proposed two-layer Rotman lens can improve the performances such as efficiency and beam pattern. Then, the two-layer design has been expanded to a Rotman lens with an 8-layer PCB substrate. The performance of the lens was verified from the simulated and measured results. The insertion loss and the radiation patterns were obtained from calculation and measurement. These results indicate that the proposed design would be useful for implementing beamforming system in packaging technologies such as SiP.