To provide a method for producing a polyolefin microporous film suitable for a separator for a battery.

In the method for producing the polyolefin microporous film, following steps are carried out: a step of preparing a solution including 5-70 pts.wt. of a polyolefin composition which contains polyolefin with 5105 or more of a viscosity-average molecular weight and polyolefin with less than 5105 of a viscosity-average molecular weight, and 30-95 pts.wt. of a mixed solvent which contains a solvent (A) with 200C of boiling point, and a volatile solvent (B) with 200C of boiling point; a step of forming a gel-like composition by heating, extruding through a die, and cooling the solution; a step of removing the solvent (B); a step of stretching; and a step of removing the solvent (A). A content of the solvent contained in the gel-like composition, after the step of removing the solvent (B), and before the step of stretching, is controlled to 10-80 wt.%.