To provide a polyolefin-based fiber having a little unevenness of the fiber, fluff and the like by significantly stabilizing a step for producing the polyolefin-based fiber by using an oil having highly uniform adhesion in a direct spin-draw method of the polyolefin-based fiber, and capable of being sufficiently extended so as to follow the drawing.

This polyolefin-based fiber has 0.1-5.0 wt.% straight oil having 0-10° contact angle to a polyolefin attached thereto. The method for producing the polyolefin-based fiber is the direct spin-draw method comprising melt- spinning a polyolefin resin, cooling the spun filament, imparting the strait oil having 0-10° contact angle to the polyolefin thereto, and continuously drawing the spun filament with the oil by hot rollers without winding the spun filament once.