As shown by the following reaction formula, disclosed is a fluorine-containing hydroxyaldehyde production method, including the step of obtaining a fluorine-containing hydroxyaldehyde represented by the general formula (1) by reacting a fluorine-containing ketone represented by the general formula (4) and an aldehyde represented by the general formula (5) in the presence of an organic base selected from a heterocyclic compound which contains a nitrogen atom in its ring or a tertiary amine. By this production method, it is possible to obtain the fluorine-containing hydroxyaldehyde in a high yield. Furthermore, it is possible to easily obtain in high yields a fluorine-containing propanediol, which is a derivative of this fluorine-containing hydroxyaldehyde, and a fluorine-containing alcohol monomer by using the same. ##STR00001##

The present invention aims to provide a water-absorbing resin crosslinking agent which is excellent in safety and which can effectively crosslink a water-absorbing resin at low temperatures to produce a water-absorbing agent having a high water absorption capacity. The present invention also aims to provide a water-absorbing agent produced by crosslinking a water-absorbing resin with the water-absorbing resin crosslinking agent, and a method for producing the water-absorbing agent. The present invention may include a water-absorbing resin crosslinking agent containing a halohydrin compound having one halohydrin group represented by the following formula (1) in its molecule:

##STR00001##

wherein A represents a single bond or an alkylene group; R.sup.1 represents a hydrogen atom or an alkyl group; and X represents a chlorine atom or a bromine atom.