The mode-division multiplexer/demultiplexer (MMUX/DeMMUX) is the crucial component for the implementation of mode-division multiplexing (MDM) transmission. We propose an on-chip two-mode MMUX/DeMMUX based on adiabatic couplers. Thanks to the principle of mode evolution. the proposed MMUX possesses advantages of broadband operation and high tolerance of fabrication error. https://www.tourettebrewing.com/