The present invention is to provide a skin external preparation with good moisture retention, a rough skin improving effect, and an improved feeling in use. A skin external preparation comprising a polyoxyalkylene glycol/polyethylene glycol copolymer alkyl ether derivative represented by the below-described general formula (I):(formula I) Y—{O(EO)a/(AO)b—R}k  (I) (In the formula, Y is the residue given by removing hydroxyl groups from a polyhydric alcohol having 3 to 6 hydroxyl groups, and k is the number of hydroxyl groups of the polyhydric alcohol. EO is an oxyethylene group; AO is an oxyalkylene group having 3 to 4 carbon atoms, and 1≦a≦70, 1≦b≦70. The percentage of the oxyethylene groups with respect to the sum of the oxyalkylene groups having 3 to 4 carbon atoms and the oxyethylene groups is 20 to 100 mass %. The oxyalkylene group having 3 to 4 carbon atoms and the oxyethylene group are added randomly. Rs are either identical to or different from each other, and they are hydrocarbon groups having 1 to 4 carbon atoms.)