Provided is a mask having a built-in adsorptive membrane, the mask including: a mask body having the built-in adsorptive membrane for adsorbing foreign substances contained in air; and a hanger band fixed to the mask body to be hung and fixed to the ear, wherein the adsorptive membrane comprises: a support member having a plurality of first pores; and a first adsorptive member that is stacked on the support member and has a plurality of second pores formed therein and that is made by accumulating ion exchange nanofibers for adsorbing ionic foreign substances in the foreign substances.