The present invention provides an oily base for a cosmetic comprising an ester compound made from a multivalent alcohol and a fatty acid, characterized in that the ester compound is made from pentaerythritol and isononanoic acid and a molar ratio of a pentaerythritol residue and an isononanoic acid residue in the ester compound is 1.0:2.3 to 1.0:4.0. The oily base for a cosmetic of the present invention has proper oily feeling with moistness, no sticky feeling, excellent adhesion to the skin and safety to the skin, and excellent compatibility with oil agents, among others, silicone oil. Furthermore, upon blending the present oily base in a cosmetic, besides having proper emollient property and moisturizing property, the cosmetic exhibits smooth feeling on use, excellent adhesion to the skin and safety to the skin, excellent cosmetic effect-holding ability, and storage stability.