An insulating resin composition for a DC power cable, the resin composition comprising: (A) 100 parts by mass of a low-density polyethylene having a complex viscosity η* 100 , which is measured at 130°C and a frequency of 100 rad/s, of 600 to 1,300 Pa s, wherein a ratio (η* 0.1 /η* 100 ) of a complex viscosity η* 0.1 , which is measured at 130°C and a frequency of 0.1 rad/s, to the complex viscosity η* 100 is 4 or more; (B) 5 to 12 parts by mass of a modified polyethylene obtained by grafting a polyethylene with at least one modifying monomer selected from unsaturated organic acids and derivatives thereof, wherein the component (B) is a modified polyethylene obtained by grafting a polyethylene with maleic anhydride (MAH); and (C) 0.01 to 0.8 parts by mass of a stabilizer including a mixture of 40% to 60% by weight of a hindered phenol antioxidant and 60% to 40% by weight of a thioether antioxidant, wherein the hindered phenol antioxidant includes tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and wherein the thioether antioxidant includes 4,4'-thiobis-(3-methyl-6-t-butylphenol) and 2,2'-thiobis-(4-methyl-6-t-butylphenol), wherein an amount of carbonyl groups introduced into the resin composition through the component (B) is 7 × 10 -6 to 1.3 × 10 -5 mol/g relative to a total mass of the component (A), the component (B), and the component (C), wherein the complex viscosity is measured by using an ARES strain-controlled rotational rheometer (TA Instruments) with a parallel plate interval of 1.7 mm. (A) 100 parts by mass of a low-density polyethylene having a complex viscosity η* 100 , which is measured at 130°C and a frequency of 100 rad/s, of 600 to 1,300 Pa s, wherein a ratio (η* 0.1 /η* 100 ) of a complex viscosity η* 0.1 , which is measured at 130°C and a frequency of 0.1 rad/s, to the complex viscosity η* 100 is 4 or more; (B) 5 to 12 parts by mass of a modified polyethylene obtained by grafting a polyethylene with at least one modifying monomer selected from unsaturated organic acids and derivatives thereof, wherein the component (B) is a modified polyethylene obtained by grafting a polyethylene with maleic anhydride (MAH); and (C) 0.01 to 0.8 parts by mass of a stabilizer including a mixture of 40% to 60% by weight of a hindered phenol antioxidant and 60% to 40% by weight of a thioether antioxidant, wherein the hindered phenol antioxidant includes tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, and wherein the thioether antioxidant includes 4,4'-thiobis-(3-methyl-6-t-butylphenol) and 2,2'-thiobis-(4-methyl-6-t-butylphenol), wherein an amount of carbonyl groups introduced into the resin composition through the component (B) is 7 × 10 -6 to 1.3 × 10 -5 mol/g relative to a total mass of the component (A), the component (B), and the component (C), wherein the complex viscosity is measured by using an ARES strain-controlled rotational rheometer (TA Instruments) with a parallel plate interval of 1.7 mm. <EOS>