A resin composition, configured to have a polymer, and at least one component selected from among acidic compounds, basic compounds and compounds reactable with acid, wherein the polymer comprises at least one monomer-derived structural unit having the structure represented by formula, or below, after the resin composition is stored at 40°C for 30 days, the decomposition rate of the structure represented by formula, or in the polymer is 20% or lower, the decomposition rate of the structure represented by formula, or is defined as: decomposition rate = measured solid acid value a − theoretical solid acid value b / theoretical solid acid value c × 100 theoretical solid value = ∑ 561 ∗ 100 / Mwi ∗ wi wherein, "wi" is the mass fraction of acidic functional group-containing monomer (i) of a copolymer, and "Mwi" indicates the molecular weight of the acidic functional group-containing monomer, the acidic functional group-containing monomer (i) is produced when the structure represented by formula, or is decomposed, and the measured solid acid value (a) is according to the following method: in a beaker, approximately 4.0 grams of a sample (A (g)) is weighed, into which 50 mL of a solution containing toluene and 95% ethanol at a ratio of 50/50 was added, the mixture is put into an airtight container and stirred for 5 minutes, a Hiranuma automatic titrator (AutoTitrator COM-1600) is used to perform potentiometric titration with a 0.5 mol/L potassium hydroxide solution (ethanol solution), having a factor (f) of 1.003 at 20°C, the end point is set at the maximum inclination point of the titration curve (titration volume = B (mL), titer of the KOH solution = f), the same procedure is conducted on a blank sample (titration volume = C (mL)), and the acid value is calculated by the following equation, solid acid value mg KOH / g = B − C × 0.5 × 56.11 × f / A / solid component, Wherein, in the above formulas, "X" is an ether oxygen atom, sulfide sulfur atom or amine nitrogen atom; R 1 and R 2 are each a hydrogen atom or a C1 to C10 alkyl group; R 3 and R 5 are each a C1 to C20 alkyl, cycloalkyl or aryl group; and R 4 and R 6 are each a C1 to C10 alkylene group. a polymer, and at least one component selected from among acidic compounds, basic compounds and compounds reactable with acid, wherein the polymer comprises at least one monomer-derived structural unit having the structure represented by formula, or below, after the resin composition is stored at 40°C for 30 days, the decomposition rate of the structure represented by formula, or in the polymer is 20% or lower, the decomposition rate of the structure represented by formula, or is defined as: decomposition rate = measured solid acid value a − theoretical solid acid value b / theoretical solid acid value c × 100 theoretical solid value = ∑ 561 ∗ 100 / Mwi ∗ wi wherein, "wi" is the mass fraction of acidic functional group-containing monomer (i) of a copolymer, and "Mwi" indicates the molecular weight of the acidic functional group-containing monomer, the acidic functional group-containing monomer (i) is produced when the structure represented by formula, or is decomposed, and the measured solid acid value (a) is according to the following method: in a beaker, approximately 4.0 grams of a sample (A (g)) is weighed, into which 50 mL of a solution containing toluene and 95% ethanol at a ratio of 50/50 was added, the mixture is put into an airtight container and stirred for 5 minutes, a Hiranuma automatic titrator (AutoTitrator COM-1600) is used to perform potentiometric titration with a 0.5 mol/L potassium hydroxide solution (ethanol solution), having a factor (f) of 1.003 at 20°C, the end point is set at the maximum inclination point of the titration curve (titration volume = B (mL), titer of the KOH solution = f), the same procedure is conducted on a blank sample (titration volume = C (mL)), and the acid value is calculated by the following equation, solid acid value mg KOH / g = B − C × 0.5 × 56.11 × f / A / solid component, Wherein, in the above formulas, "X" is an ether oxygen atom, sulfide sulfur atom or amine nitrogen atom; R 1 and R 2 are each a hydrogen atom or a C1 to C10 alkyl group; R 3 and R 5 are each a C1 to C20 alkyl, cycloalkyl or aryl group; and R 4 and R 6 are each a C1 to C10 alkylene group.