Electrochemical element separator and electrochemical element obtained using same

The purpose of the present invention is to provide: an electrochemical element separator that has excellent manufacturing stability, is without pinholes and has low internal resistance; and an electrochemical element that is obtained using the same. Provided is an electrochemical element separator comprising: a nonwoven substrate; and an inorganic particle layer that contains inorganic particles. The electrochemical element separator is characterized: in that a main constituent of the nonwoven substrate is synthetic resin fibers with an average fiber diameter of 1 to 20 μｍ; in that the inorganic particle layer includes an inorganic particle layer A that contains magnesium hydroxide with an average particle diameter of 2.0 to 4.0 μｍ, and an inorganic particle layer B that contains magnesium hydroxide with an average particle diameter of at least 0.5 μｍ and less than 2.0 μｍ; and in that the inorganic particle layer A and the inorganic particle layer B are stacked in this order on one surface of the nonwoven substrate; or in that the inorganic particle layer A is provided on one surface of the nonwoven substrate and the inorganic particle layer B is provided on the other surface thereof. The electrochemical element is obtained using the electrochemical element separator.