Insulating resin composition for electric power cable, electric power cable, and electric power cable connecting part

An insulating resin composition for electric power cable comprising:

• a polypropylene resin (A) which is a propylene-based polymer;
• and a styrene-based thermoplastic elastomer (B), wherein
• a temperature characteristic curve of loss tangent tan δ obtained by dynamic viscoelasticity measurement at a frequency of 100 rad/s has a high-temperature-side temperature region in which the loss tangent tan δ is 0.1 or more and 0.4 or less, and a low-temperature-side temperature region in which the loss tangent tan δ is less than 0.1;
• and
• a highest temperature of the high-temperature-side temperature region is 240° C. or more;
• and
• a content proportion of styrene contained in the insulating resin composition for electric power cable is 12.5% by mass or more and 30% by mass or less.