A new type of grounded coplanar waveguide (GCPW) to rectangular waveguide transition in an LTCC multi-layer structure for 60 GHz applications is proposed in this letter. The GCPW and rectangular waveguide are fully integrated on the same substrate, and the ground wall of the rectangular waveguide is made up of a staggered via fence. The transition is accomplished by inserting a bent short stub. We analyze and prove the novel transition structure by applying an equivalent circuit model. Measured results for a single transition show that the insertion loss is 0.345 dB at 59 GHz and the bandwidth is 6.3 GHz. The proposed transition structure with very low loss at a large bandwidth is very suitable for a SiP of 60 GHz WPAN applications.