A quaternary ammonium compound of the present invention is a quaternary ammonium compound represented by general formula (I) or (I') ##STR00001## (wherein, A represents a linear alkyl group having 1 to 4 carbon atoms, a branched alkyl group having 2 to 4 carbon atoms, a linear alkyl group having 1 to 4 carbon atoms and a hydroxyl group, or a branched alkyl group having 2 to 4 carbon atoms and a hydroxyl group, R.sub.1 to R.sub.3 may be the same or different and represent a linear or branched alkyl group having 1 to 12 carbon atoms, one of R.sub.4 to R.sub.8 represents CO.sub.2.sup.- or SO.sub.3.sup.-, while no more than three of the remaining R.sub.4 to R.sub.8 represent a group selected from the group consisting of a hydroxyl group and an alkoxy group having 1 to 4 carbon atoms, and other R.sub.4 to R.sub.8 represent a hydrogen atom, one of R'.sub.4 to R'.sub.8 represents CO.sub.2H or SO.sub.3H, no more than three of the remaining R'.sub.4 to R'.sub.8 represent a group selected from a protected hydroxyl group and an alkoxy group having 1 to 4 carbon atoms, while other R'.sub.4 to R'.sub.8 represent a hydrogen atom, and X.sup.- represents an anion capable of forming a salt with a quaternary ammonium group).