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, wherein the shutdown shrinkage temperature in the TD indicates the temperature at the inflection point of the length in the TD and the maximum shrinkage temperature in the TD indicates the temperature at which the length of a sample is smallest in the TD; a rate difference less than 25% between a shutdown shrinkage rate and a maximum shrinkage rate in the TD, wherein the shutdown shrinkage rate in the TD is the shrinkage rate of the length in the TD of the microporous membrane at the shutdown shrinkage temperature in the TD and is calculated using the length in the TD at room temperature as a reference, and wherein the maximum shrinkage rate in the TD is the shrinkage rate of the length in the TD of the microporous membrane at the maximum shrinkage temperature in the TD and is calculated using the length in the TD at room temperature as a reference; a pin puncture strength at a membrane thickness of 16 μm being not less than 400 gf, wherein the pin puncture strength is determined using a needle being 1 mm in diameter and having a spherical surface, with a radius of curvature R being 0.5 mm at the tip, to puncture a microporous membrane at a rate of 2 mm/sec and measuring the maximum load immediately prior to penetration; and a 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)), wherein the air permeation resistance is measured using an air permeability meter, and wherein the air permeation resistance at a membrane thickness of 16 μm refers to the air permeation resistance P 2 calculated by the formula P 2 =(P 1 ×16)/T 1, where P 1 is the air permeation resistance measured in accordance with JIS P 8117 for a microporous membrane having a membrane thickness T 1; wherein a content of a polyolefin having a molecular weight of not greater than 5.0 × 10 5 is 45 wt.% to 63 wt.%, and a content of a polyolefin having a molecular weight of not less than 1.0 × 10 6 is 21 wt.% to 40 wt.%. 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, wherein the shutdown shrinkage temperature in the TD indicates the temperature at the inflection point of the length in the TD and the maximum shrinkage temperature in the TD indicates the temperature at which the length of a sample is smallest in the TD; a rate difference less than 25% between a shutdown shrinkage rate and a maximum shrinkage rate in the TD, wherein the shutdown shrinkage rate in the TD is the shrinkage rate of the length in the TD of the microporous membrane at the shutdown shrinkage temperature in the TD and is calculated using the length in the TD at room temperature as a reference, and wherein the maximum shrinkage rate in the TD is the shrinkage rate of the length in the TD of the microporous membrane at the maximum shrinkage temperature in the TD and is calculated using the length in the TD at room temperature as a reference; a pin puncture strength at a membrane thickness of 16 μm being not less than 400 gf, wherein the pin puncture strength is determined using a needle being 1 mm in diameter and having a spherical surface, with a radius of curvature R being 0.5 mm at the tip, to puncture a microporous membrane at a rate of 2 mm/sec and measuring the maximum load immediately prior to penetration; and a 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)), wherein the air permeation resistance is measured using an air permeability meter, and wherein the air permeation resistance at a membrane thickness of 16 μm refers to the air permeation resistance P 2 calculated by the formula P 2 =(P 1 ×16)/T 1, where P 1 is the air permeation resistance measured in accordance with JIS P 8117 for a microporous membrane having a membrane thickness T 1; wherein a content of a polyolefin having a molecular weight of not greater than 5.0 × 10 5 is 45 wt.% to 63 wt.%, and a content of a polyolefin having a molecular weight of not less than 1.0 × 10 6 is 21 wt.% to 40 wt.%.