An aqueous dispersion of polyurethane resin is obtained by a chain elongation reaction in water wherein (C) at least one chain extender selected from a group consisting of water-soluble polyamines, hydrazine and derivatives thereof is added to a dispersion liquid obtained by emulsifying and dispersing a mixture in water. The mixture comprises: (B) at least one compound selected from the phosphorous compounds represented by the following formula (1) and (A) an urethane prepolymer and/or a neutralized urethane prepolymer material which has an isocyanate group at the terminal. The urethane prepolymer of component (A) is an urethane prepolymer obtained from (a1) an organic polyisocyanate and (a2) a polymeric polyol. The neutralized urethane prepolymer material of component (A) is a neutralized material obtained by neutralizing an urethane prepolymer which is obtained by further using (a3) a compound having an anionic hydrophilic group and at least two active hydrogens in a molecule together with the components (a1) and (a2).