A halogen-free flame-retardant resin composition includes 100 parts by, weight of base polymer of polyolefin resin, not less than 50 parts by weight and not more than 250 parts by weight of metal hydroxide, not less than 1 part by weight and not more than 50 parts by weight of calcium borate, not less than 1 part by weight and not more than 50 parts by weight of zinc stannate, and less than 30 seconds of burning time after removal of flame in a vertical flame test complying with CODE 895 OR 3rd edition, appendix 6 of the UIC standard.