To obtain the subject composition comprising a styrenic resin, a specific cationic polymer and antistatic agent, excellent in antimicrobial property and impact resistance, thermally not colored and useful for toilet seats, etc.

This antimicrobial resin composition comprises (A) 5-99wt.% of a styrenic resin, (B) 0.9-50wt.% of a cationic polymer having at least one kind of cationic structure units selected from the group consisting of groups of formula I to formula III [R1 is a 2-8C alkylene; R2, R3 are each a 1-4C alkyl; R4 is a 1-12C alkyl, a 6-12C arylalkyl, an alicyclic alkyl; X is CH3SO3, C2H5SO3, C3H7SO3, etc.; R5 is H, methyl; (m) is 0, 1] and (C) 0.1-30wt.% of an antistatic agent not having the cationic structural units used in the component B. The antimicrobial resin composition preferably further contains (D) an antimicrobial agent in an amount of 0.01-30 pts.wt. per 100wt.% of the total amount comprising 50-99wt.% of the component A and 50-1wt.% of the component B.