To obtain a polyester monofilament exhibiting excellent stain-proofing property against oily tacky materials, having excellent durability and flexing abrasion resistance and useful as a paper machine wire, etc., by specifying a receding contact angle to be smaller than a prescribed level in the measurement of a dynamic contact angle between the monofilament surface and ion- exchanged water.

This monofilament made of polyethylene terephthalate or the like has a receding contact angle of <50° or an advancing contact angle of <80° in dynamic contact angle between the monofilament surface and ion- exchanged water measured by Wilhelmy method. The polyester monofilament preferably contains 0.2-30 wt.% of a polyether ester amide and has a flexing abrasion breakage cycle satisfying the formula (C is a flexing abrasion breakage cycle number; D is minor diameter of the monofilament and is 0.05-1.00 mm).