A simple and low-cost shared aperture antenna module for 5G N78 and N257 applications is proposed. This module integrates a microwave (MW) patch antenna and a millimeter wave (MMW) substrate-integrated waveguide (SIW) slot antenna. The MW part employs splits etched on the patch and shorting vias to excite TM01, TM20, and TM21 modes simultaneously and generate a wide band covering N78 band. In the MMW part, beveled SIW cavities with additional metal vias are set on the same substrate of the patch antenna and extend the bandwidth of the slot antennas covering N257 band. The shared-aperture antenna module provides high port isolations, and high and flat gains for both bands. Moreover, the MMW beam scanning is manipulated in the E- and H-plane. A prototype is designed, implemented and measured for verification.