Abstract: An object of the present invention is to provide an agent for promoting undifferentiation that dissolves a drug, as DMSO or the like does, but is capable of promoting undifferentiation without inducing cell differentiation when added to a medium. The agent for promoting undifferentiation of the present invention has an aprotic zwitterion represented by the following formula (1) wherein A is an anion selected from the group consisting of SO3?, —COO?, —OP?O(H)O?, —OP?O(CH3)O? and —OP?O(OR3)O?, R1 is an alkyl group having 1 to 8 carbon atoms and optionally containing one or two oxygen atoms in the molecular chain, R2 is an alkylene group having 3 to 5 carbon atoms, and R3 is hydrogen or an alkyl group optionally having a heteroatom in the molecular chain.