A modifier for resin has an average particle size of 20 μm or more, wherein particles having an average particle size of 10 μm or less account for less than 30% by mass of the modifier, and particles having an average particle size of 10 μm or less account for 30% by mass or more of the modifier after irradiating the modifier with ultrasonic wave of 40 W for 5 minutes. Also a resin composition comprises 1 to 40% by mass of the modifier for resin and 99 to 60% by mass (the total amount of both components is 100% by mass) of a thermoplastic resin or a curable resin, and a molded article is produced by molding the same.