A method for producing a multi-wavelength semiconductor laser device includes the steps of: forming a nitride epitaxial layer on a substrate for growth of a nitride single crystal; separating the nitride epitaxial layer from the substrate; attaching the separated nitride epitaxial layer to a first conductivity-type substrate; selectively removing the nitride semiconductor epitaxial layer to expose a portion of the first conductivity-type substrate and to form a first semiconductor laser structure; and sequentially forming second and third semiconductor laser structures on the exposed portion of the first conductivity-type substrate.