PURPOSE: To obtain a resin composition with outstanding mechanical properties and low water absorptivity, by incorporating a polyamide resin with respective specific amounts of a polyolefin resin, EP rubber, and polyoctenylene resin.

CONSTITUTION: The objective resin composition can be obtained by incorporating (A) 100pts.wt. of a polyamide resin with the number of amide groups 8W17 per 100 carbon atoms (e.g. nylon 6) with (B) 1W100pts.wt. of a polyolefin resin (e.g. polypropylene), (C) 1W100pts.wt. of an EP rubber with an ethylene unit content 30W90mol%, a copolymer from ethylene and ≥3C α-olefin, and (D) 1W100pts.wt. of a polyoctenylene resin with one double bond per 8 carbon atoms and molecular weight ≥10,000.