The present invention relates to a method for producing a semi-IPN composite, the method including polymerizing a hydrophilic monofunctional acrylate (b1) and a polyfunctional acrylate (b2) in a solution of a polyurethane (A) prepared using an aliphatic polyisocyanate and/or an alicyclic polyisocyanate as a raw material. The present invention also relates to a method for producing a synthetic leather that includes a layer obtained by drying the semi-IPN composite obtained by the above production method. One object of the present invention is to provide a method for producing a semi-IPN composite excellent in stain resistance. The semi-INP composite obtained by the production method of the present invention is excellent in stain resistance. Therefore, the semi-IPN composite can be used particularly preferably for skin and topcoat layers of synthetic leathers for vehicles.