To provide a degradable fishing line having improved heat resistance and a balance with respect to formability of spinning, drawing, etc., physical properties in use, chemical degradation after abandonment, by using a lactone resin or the like subjected to irradiation under specific conditions.

This degradable fishing line is obtained by spinning a lactone resin (a) such as a (co)polymer of -caprolactone, -butyrolactone or the like alone or a lactone-containing resin (c) composed of the lactone resin (a) and another synthetic and/or a biociegraclable resin (e.g. an aliphatic polyester, cellulose, etc.), (b) such as a natural polymer, etc., or a lactone-containing resin composition comprising the lactone-containing resin (c) and an resin additive (d) such as a plasticizer, etc. The constitutent component lactone resin alone or together with one or more constituent components are subjected to irradiation to give the fishing line having ≥5.0 g/d tensile strength, ≥4.0 g/d knot strength, ≥10% initial elongation ratio and ≥150 g/d initial modulus of elongation.