A separator, a method of manufacturing the separator, and an electrochemical device including the separator. The separator includes: a porous substrate; and an inorganic particle layer formed on at least one surface of the porous substrate, wherein a release rate of the inorganic particle layer is 70% or more when measured by immersing the separator in a water tank at room temperature and then subjecting the separator to sonication under conditions of a frequency of 40 kHz, an output of 1,000 W, and an application time of 60 seconds.