A monofilament obtained by smelt-spinning and stretching of a vinylidene fluoride resin is subjected to a high-temperature relaxation treatment for an extremely short period of 0.05-0.5 sec. within a high-temperature heating oil bath at a temperature of 140-175° C., thereby producing a vinylidene fluoride resin monofilament, which comprises a vinylidene fluoride resin having an inherent viscosity of at least 1.40 dl/g, and has a knot strength (JIS L1013) of at least 600 MPa and excellent anti-twist property represented by a twist index of at least 0.90 when measured after the monofilament being subjected to application for 1 minute of a tensile load equal to approximately 50% of a maximum tensile load (JIS K7113), removal of the load, and standing for 3 hours.