A method for producing a polymer has: a polymerization step of polymerizing at least a conjugated diene monomer in a hydrocarbon solvent using an organolithium compound as a polymerization initiator, and obtaining a polymer; and, following steps (1) to (4), successively performing after the polymerization step: (1) a step of mixing an acid and water of 20 to 300 parts by mass into the solution containing the polymer of 100 parts by mass, (2) a step of adjusting an amount of the water to 10 parts by mass or less based on 100 parts by mass of the solution containing the polymer, (3) a step of adding a carbon oxide gas and/or a compound to be decarboxylated to the solution containing the polymer, and (4) a step of removing a solvent from the solution containing the polymer until a concentration of the polymer reaches 95 mass % or more.

Provided are an actinic ray-sensitive or radiation-sensitive resin composition containing a resin including a specific repeating unit represented by formula (1) and a specific repeating unit represented by formula (2), at least one of the repeating unit represented by formula (1) or the repeating unit represented by formula (2) having a group derived from at least one metal compound selected from the group consisting of a metal complex, an organometallic salt, an inorganic metal compound, and an organometallic compound, a resist film formed from the actinic ray-sensitive or radiation-sensitive resin composition, a pattern forming method that uses the actinic ray-sensitive or radiation-sensitive resin composition, and a method for producing an electronic device.

Provided are an actinic ray-sensitive or radiation-sensitive resin composition containing a resin including a specific repeating unit represented by formula (1) and a specific repeating unit represented by formula (2), at least one of the repeating unit represented by formula (1) or the repeating unit represented by formula (2) having a group derived from at least one metal compound selected from the group consisting of a metal complex, an organometallic salt, an inorganic metal compound, and an organometallic compound, a resist film formed from the actinic ray-sensitive or radiation-sensitive resin composition, a pattern forming method that uses the actinic ray-sensitive or radiation-sensitive resin composition, and a method for producing an electronic device.