Provided are: a water-soluble triaryl phosphine for a palladium catalyst that can be efficiently and easily recovered and that has high selectivity in a telomerization reaction; an ammonium salt thereof; and a method for efficiently producing same. Specifically, provided are: bis(6-methyl-3-sulphophenyl)phenylphosphine; diammonium bis(6-methyl-3-sulphophenyl)phenylphosphinate obtained by reacting the phosphine with a ternary amine having 3-27 carbon atoms in a group bonded to one nitrogen atom; and a method for producing same.