An oil-in-water type emulsion sunscreen cosmetic composition having improved ultraviolet blocking capability, excellent emulsion stability and good usability. The oil-in-water type emulsion sunscreen cosmetic composition is characterized by containing (A) 1-7.5% by mass of octyl methoxycinnamate, (B) 0.5-4% by mass of t-butyl methoxybenzoyl methane and/or 2-hydroxy-4-methoxybenzophenone, (C) 0.5-3% by mass of a polyoxyethylene-polyoxyalkylene alkyl ether block polymer having a specific structure and (D) not less than 10% by mass of a nonpolar oil relative to the total amount of the oil component. The oil-in-water emulsion sunscreen cosmetic composition is also characterized by having an average emulsion particle diameter of not more than 700 nm.