A method for producing a compound represented by formula (P1): (B1f)mp(A1)np, wherein B1f is RfCOO, Rf is a hydrocarbon having one or more fluorine atoms, A1 is a group excluding H, mp is (valence of A1)×np and is 1 or 2, np is mp/(valence of A1) and is 1, A1 has a valence of 1 or 2, the method comprising step A of reacting a compound represented by formula (S1): (B1f)(R1), wherein B1f is as defined above, and R1 is an organic group, and a compound represented by formula (S2): (A1)ms2(B2)ns2, wherein A1 is as defined above, B2 is OH, CO3, or HCO3, ms2 is (valence of B2)×ns2/(valence of A1) and is 1 or 2, and ns2 is (valence of A1)×ms2/(valence of B2) and 1 or 2, or a hydrate thereof. Such a method is a novel production method of a fluorinated carboxylic acid salt compound (preferably a fluorinated carboxylic acid salt compound having a low water content).