A separator is provided which includes: a separator base including a porous polymer substrate having a plurality of pores, and a porous coating layer positioned on at least one surface of the porous polymer substrate and containing a plurality of inorganic particles and a binder polymer positioned on the whole or a part of the surface of the inorganic particles to connect the inorganic particles with one another and fix them; and a porous adhesive layer positioned on at least one surface of the separator base and including polyvinylidene fluoride-co-hexafluoropropylene containing vinylidene fluoride-derived repeating units and hexafluoropropylene-derived repeating units, wherein the ratio of the number of the hexafluoropropylene (HFP)-derived repeating units (HFP substitution ratio) based on the total number of the vinylidene fluoride-derived repeating units and the hexafluoropropylene-derived repeating units is 4.5% to 9%. An electrochemical device including the separator is also provided.