A method for producing a porous cross-linked polymer sheet capable of slicing quickly is provided. This method comprises a step for obtaining a porous cross-linked polymer by forming and polymerizing an HIPE, a step for dehydrating the porous cross-linked polymer, and a step for subsequently slicing the dehydrated porous cross-linked polymer. According to this invention, by performing the step of dehydration prior to the conventional step of slicing, it is made possible to prevent the porous cross-linked polymer from adhering to the blade and the guides provided for a slicer, and allow the slicing to be attained quickly. By removing the salt from the polymer, it is further made possible to prevent a production device from gathering rust and the porous cross-linked polymer from permitting adhesion of rust thereto.