A resin composition which exhibits an excellent heat-retaining property without reducing transparency when it is used as an agricultural film.The resin composition comprises 100 parts by weight of a resin and 1 to 20 parts by weight of a heat-retaining agent which is represented by the following formula (1) and has a difference between the molar ratio obtained from 2θ of the (110) plane by an X-ray diffraction method and the molar ratio obtained by chemical analysis of not more than 0.7 7 (the molar ratio is an Mg/Al2 value). MgXAl2(OH)2X+4(CO3)·mH2O (1)(In the above formula, X satisfies 4.0 < X ≦ 6.5, and "m" is 0 or a positive number.)
