PURPOSE: To obtain a permanently antistatic agent with which a thermoplastic synthetic resin composition satisfactory in permanently antistatic properties and mechanical properties can be obtained, by using a specific polyurethane and a polyacetal in combination.

CONSTITUTION: The subject permanent antistatic agent comprises a polyurethane (A) having a surface resistivity of 1014Ω or lower and a polyacetal (B) in a weight ratio of 1:10 to 40:1. This " agent is mixed with a thermoplastic resin (C) to give a composition in which the contents of the ingredients (A), (B), and (C) are 2-40wt.%, 1-20wt.%, and 60-97wt.%, respectively. The ingredient (C) is preferably a (co)polymer of a vinyl compound, in particular, a thermoplastic polyolefin or styrene resin. This composition may contain a dispersant, preferably a polyolefin containing hydroxyl, epoxy, or acid anhydride groups.