To provide a heat-resistant complex polyolefin microporous film, which can be easily handled, has both shutdown characteristics and heat resistance, has a relatively large caliber that has good gas permeability that is advantageous for rapid charge and discharge, and thus serves as a separator for lithium ion secondary batteries and to provide a method for producing the heat-resistant complex polyolefin microporous film.

To make use of the characteristics of a polyolefin microporous film including its contribution to rapid charge and discharge and good maintenance of the capacity as a separator for lithium ion secondary batteries, and good gas permeability and to provide heat resistance, the heat-resistant complex polyolefin microporous film and the method for producing the same are characterized in that a hole being in communication with the front and back of a polyolefin microporous film with good gas permeability and a relatively large caliber is embedded in advance in a substance that can be extracted with a solvent, a heat-resistant polymer coating film having uniform thickness is formed on the front and back of the film by a coating method for simultaneous coating of both sides, and then the resin enclosing the hole being in communication with the front and back is extracted with a solvent. The heat-resistant complex polyolefin microporous film is also provided as a separator for lithium ion secondary batteries.