To obtain a resin composition excellent in electric conductivity, mechanical properties, heat stability, and moldability, particularly in moldability in molding a small article by blending a polyacetal resin, carbon black and a heat stabilizer comprising a quinoline compound each in a specified amount.

A polyacetal resin in a amount of 100 pts.wt. is blended with carbon black in an amount of 1-20 pts.wt. and a heat stabilizer comprising quinoline compound(s) represented by formula I [R1, R2 and R3 are each a 1-3C alkyl; and Z is OR4 (R4 is a 1-3C alkyl)], formula II (n is an integer) and formula III [A and D are each H, OH or a 1-3C alkyl; B is H or a 1-3C alkyl; E is H or OH; G is H, OH, a 1-3C alkyl, or a 1-3C alkoxy; and J and L are each H or OH (provided that the quinoline ring has at least five H atoms)], in an amount of 0.1-15 pts.wt. The polyacetal resin suitably used comprises one having a melt flow rate of at least 4 g/10 min.