A photopolymerization initiator which is a compound having a structure in which one or more carbonyl groups that link to a carbon atom are further directly bonded to an aromatic ring of an aromatic acyl group that bonds to a phosphorus atom in an acylphosphine oxide structure. A producing method of a photopolymerization initiator produces the photopolymerization initiator. In a polymerizable composition and an ink jet recording method, the photopolymerization initiator is used. Furthermore, an acylphosphine oxide compound has a partial structure represented by Formula 1 or Formula 2.