The present invention relates to an acrylamide-based mesoporous polymer and its preparation method, where the acrylamide-based mesoporous polymer is fabricated by a simple preparation method to have uniform minute pores controllable in pore size and thereby applicable to a wide variety of fields. The acrylamide-based mesoporous polymer includes at least one of a defined repeating unit and contains a plurality of pores having a diameter of 2.0 to 10.0 nm in the solid state.