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 5.0×1013 to 1.0×1016 &OHgr;·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: [MgxCay]·Alz·(OH)2·An−p·mH2O  wherein 0.2≦z/(x+z)≦0.6; 0.01≦y/(x+z)≦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 &mgr;m and a thickness of 0.02 to 0.08 &mgr;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.