This polyamide resin composition includes a polyamide resin and a copper-based heat-resistant stabilizing agent. The copper content in the copper-based stabilizing agent is 0.001-0.050 parts by mass with respect to 100 parts by mass of the polyamide resin. The polyamide resin includes a dicarboxylic acid-derived component unit (a) and a diamine-derived component unit (b). The dicarboxylic acid-derived component unit (a) includes an aromatic dicarboxylic acid-derived component unit or an alicyclic dicarboxylic acid-derived component unit. The diamine-derived component unit (b) includes a diamine-derived component unit (b2) represented by formula (1) in an amount of 10 mol % or more but less than 50 mol % with respect to the total number of moles of the diamine-derived component unit (b).