A chlorine-containing resin composition for covering an electric wire of the present invention, has a heat stability of not less than 240 minutes and a volume resistivity of 5.0.times.10.sup.13 to 1.0.times.10.sup.16 .OMEGA..multidot.cm when measured according to JIS K6723, and comprises: 100 parts by weight of a chlorine-containing resin, and 1.5 to 10 parts by weight of Mg--Al-based hydrotalcite-type particles having a composition represented by the formula: [Mg.sub.x Ca.sub.y ].multidot.Al.sub.z.multidot.(OH).sub.2.multidot.A.sup.n-.sub. p.multidot.mH.sub.2 O wherein 0.2.ltoreq.z/(x+z).ltoreq.0.6; 0.01.ltoreq.y/(x+z).ltoreq.0.20; x+y+z=1; p=(2(x+y-1)+3z)/n; A is a n-valent anion; and m is more than 0 and not more than 0.75, having a plate surface diameter of 0.1 to 1.0 .mu.m and a thickness of 0.02 to 0.08 .mu.m, and containing calcium at a molar ratio of Ca to a sum of Mg and Al of 0.01:1 to 0.20:1, and having a heat-resisting time of not less than 4 hours upon a chlorine-containing resin composition containing the Mg--Al-based hydrotalcite-type particles.