The present invention provides a microporous membrane having an excellent balance of temperature characteristics, shrinkage characteristics, permeability, and strength, and thereby realizes a separator for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery, having excellent performance and excellent safety. A polyolefin microporous membrane having;a temperature difference not less than 7.2° C. between a shutdown shrinkage temperature and a maximum shrinkage temperature in a TD measured by TMA;a shrinkage rate difference less than 25% between a shutdown shrinkage rate and a maximum shrinkage rate in the TD;a pin puncture strength at a membrane thickness of 16 μm being not less than 400 gf; anda ratio of pin puncture strength to air permeation resistance at a membrane thickness of 16 μm being from 2.0 to 4.0 (gf/(sec/100 cc)).