Provided are: a novel polyglycerol di-(alkyl/alkenyl) ether that is useful as a highly hydrophilic gemini surfactant and a cosmetic composition containing the polyglycerol di-(alkyl/alkenyl) ether. The polyglycerol di-(alkyl/alkenyl) ether is represented by Formula (1), where R1 and R2 are identical or different and are independently a straight- or branched-chain alkyl group or a straight- or branched-chain alkenyl group, where the alkyl group may have one or more hydroxyl groups and n indicates a number of glycerol units and is an integer of 2 or more. Formula (1) is expressed as follows:
