An E-plane beamwidth suppressed SIW H-plane Horn Antenna is presented in this paper. A novel substrate integrated corrugation structure is proposed based on the corrugation theory in traditional metal horn antennas. Necessary modifications based on the transmission line theory are made so that the corrugation maintains a low profile. Both the SIW H-plane horn and the corrugation board can be easily fabricated using printed circuit board (PCB) technology. A wide bandwidth from 26 GHz to 40 GHz together with over 100° E-plane beamwidth suppression is obtained. The measured performance of the fabricated antenna prototype is in a great agreement with the simulation. The compact structure, low profile, large bandwidth and high gain of the proposed antenna make it a competitive choice for 5G handset devices.