This invention provides a hydroxyl group-containing betaine compound and a long-chain alkyl group-containing betaine compound, both of which are highly biodegradable and useful as surfactants, bactericides, antistatic agents, softening agents, rust inhibitors, resin modifiers, synthetic intermediates, etc. The invention further provides processes for producing such betaine compounds. The hydroxyl group-containing betaine compound mentioned above can be represented by the following general formula (1) wherein R1 and R2 maybe the same or different and each represents a hydrogen atom, a C1-8 hydrocarbon group or a C1-8 hydrocarbon group having a hydroxyl group, exclusive of the case in which both of R1 and R2 respectively represent a hydrogen atom; in case neither R1 nor R2 represents a hydrogen atom, R1 and R2 may be joined to each other through a single bond or through at least one kind of element selected from the group consisting of O, S and N; R3 represents a hydrogen atom, a methyl group or a hydroxymethyl group; A represents a hydrocarbon group of 2˜25 carbon atoms.