The present invention provides an industrial method for production of silodosin, which is useful for a therapeutic agent for dysuria associated with benign prostatic hyperplasia. The production of silodosin is characterized by mixing (R)-1-(3-hydroxypropyl)-5-(2-(2-(2-(2, 2, 2-trifluoroethoxy) phenoxy) ethyl amino) propyl) indoline-7-carbonitrile (V) and N-acetyl-L-glutamic acid to yield the N-acetyl-L-glutamate salt, subsequently neutralising the N-acetyl-L-glutamate salt and hydrolyzing the same, and manufacturing intermediates used therefore. The invention also provides an industrial production method of silodosin alpha, beta and gamma crystalline forms.
