The method is for reducing a leakage path and for adjusting depth of PN junction of the InGaAsP/InP laser diode by using a melt-back phenomenon. The method comprises the steps of; (A) forming a N-InP buffer layer, an undoped InGaAsP active layer and P-InP layer; (B) etching the P-InP layer to form a P-InP pattern; (C) triggering a melt-back phenomenon to form an active-layer pattern; (D) adding a Zn dopant on a source material to form a P-type diffused region; (E) growing a N-InP layer to protect leakage current and remove an etching mask; and (F) growing a P-InP layer and L-InGaAsP layer on the P-InP layer and the N-InP layer.
