A polyamide resin composition, comprising: 100 parts by weight of an (a) polyamide resin; and 0.1 to 20 parts by weight of a (g) compound and/or its condensate that includes a hydroxyl group and an epoxy group or a carbodiimide group and has a structure expressed by General Formula: where X 1 to X 6 are identical or different and respectively represent OH, CH 3 or OR, in which a total number of OH and OR is three or more, R represents an epoxy group-including or carbodiimide group-including organic group, and n indicates a range of 0 to 20; wherein the (g) compound and/or its condensate is the product of a reaction between a (b) hydroxyl group-containing aliphatic compound and a compound having an epoxy group or a carbodiimide group, and the reaction rate of the (b) hydroxyl group-containing aliphatic compound and a compound having an epoxy group or a carbodiimide group is not lower than 20% and not higher than 70%, that reaction rate being determined by dissolving the (g) compound and/or its condensate in a solvent and calculating a reduction before and after the reaction of the epoxy group with the (b) hydroxyl group-containing aliphatic compound with regard to epoxy ring-derived peaks by 1 H-NMR measurement or a reduction before and after the reaction of the carbodiimide group with the (b) hydroxyl group-containing aliphatic compound with regard to a carbodiimide group-derived peak by 13 C-NMR measurement; and then determining the reaction rate by the following Formula: Reaction rate % = 1 − b / a × 100 where, in the above Formula, 'a' denotes a peak area of the dry-blended mixture of the (b) hydroxyl group-containing aliphatic compound and the compound having an epoxy group or a carbodiimide group as the functional group of the (c) compound containing reactive functional group with amino groups or hydroxyl group, and 'b' denotes a peak area of the (g) compound and/or its condensate. 100 parts by weight of an (a) polyamide resin; and 0.1 to 20 parts by weight of a (g) compound and/or its condensate that includes a hydroxyl group and an epoxy group or a carbodiimide group and has a structure expressed by General Formula: where X 1 to X 6 are identical or different and respectively represent OH, CH 3 or OR, in which a total number of OH and OR is three or more, R represents an epoxy group-including or carbodiimide group-including organic group, and n indicates a range of 0 to 20; wherein the (g) compound and/or its condensate is the product of a reaction between a (b) hydroxyl group-containing aliphatic compound and a compound having an epoxy group or a carbodiimide group, and the reaction rate of the (b) hydroxyl group-containing aliphatic compound and a compound having an epoxy group or a carbodiimide group is not lower than 20% and not higher than 70%, that reaction rate being determined by dissolving the (g) compound and/or its condensate in a solvent and calculating a reduction before and after the reaction of the epoxy group with the (b) hydroxyl group-containing aliphatic compound with regard to epoxy ring-derived peaks by 1 H-NMR measurement or a reduction before and after the reaction of the carbodiimide group with the (b) hydroxyl group-containing aliphatic compound with regard to a carbodiimide group-derived peak by 13 C-NMR measurement; and then determining the reaction rate by the following Formula: Reaction rate % = 1 − b / a × 100 where, in the above Formula, 'a' denotes a peak area of the dry-blended mixture of the (b) hydroxyl group-containing aliphatic compound and the compound having an epoxy group or a carbodiimide group as the functional group of the (c) compound containing reactive functional group with amino groups or hydroxyl group, and 'b' denotes a peak area of the (g) compound and/or its condensate. where X 1 to X 6 are identical or different and respectively represent OH, CH 3 or OR, in which a total number of OH and OR is three or more, R represents an epoxy group-including or carbodiimide group-including organic group, and n indicates a range of 0 to 20; wherein the (g) compound and/or its condensate is the product of a reaction between a (b) hydroxyl group-containing aliphatic compound and a compound having an epoxy group or a carbodiimide group, and the reaction rate of the (b) hydroxyl group-containing aliphatic compound and a compound having an epoxy group or a carbodiimide group is not lower than 20% and not higher than 70%, that reaction rate being determined by dissolving the (g) compound and/or its condensate in a solvent and calculating a reduction before and after the reaction of the epoxy group with the (b) hydroxyl group-containing aliphatic compound with regard to epoxy ring-derived peaks by 1 H-NMR measurement or a reduction before and after the reaction of the carbodiimide group with the (b) hydroxyl group-containing aliphatic compound with regard to a carbodiimide group-derived peak by 13 C-NMR measurement; and then determining the reaction rate by the following Formula: Reaction rate % = 1 − b / a × 100 where, in the above Formula, 'a' denotes a peak area of the dry-blended mixture of the (b) hydroxyl group-containing aliphatic compound and the compound having an epoxy group or a carbodiimide group as the functional group of the (c) compound containing reactive functional group with amino groups or hydroxyl group, and 'b' denotes a peak area of the (g) compound and/or its condensate.