The present invention relates to an oral soft capsule formulation comprising: (1) a filling material comprising dutasteride; and (2) a soft capsule film containing succinylated gelatin, a plasticizer, and a cross-linking inhibitor. The inventive soft capsule formulation can maintain superior drug dissolution stability, disintegration time and sealability of formulation, regardless of packaging and storage and storage conditions; and thus can be effectively used in the treatment of benign prostatic hyperplasia, prostate cancer, and male pattern alopecia.