A polyester monofilament package is formed by reeling a polyester monofilament comprising polyethylene terephthalate and satisfies all of the following requirements (a) to (d): (a) the coefficient of dynamic friction between yarns of the polyester monofilament being 0.13 μd or less; (b) the package end being in a tapered shape with a taper angle (0) of 75° or less; (c) the variation gradient in unreeling tension (AT) being 0.02 cN/dtex-m or less; and (d) in a part of a reeling thickness of 1 mm in the inner layer of the package, the variation in contraction stress of the polyester monofilament being 3.0 cN/dtex or less.