A polyamide/polyurethane composite filament yarn, contains a filament having a polyamide sheath component and a polyurethane eccentric core component exposed, through a neck portion of uniform width, on the surface of the filament. The filament is manufactured by a process comprising inserting, immediately before extruding from a spinneret orifice, a molten polyurethane flow, at an oblique angle from above, into a molten polyamide flow flowing down in a conduit, so that a small part of the polyurethane flow radially projects in a restricted width through the thinnest portion of the polyamide flowing flows down the inner wall of the conduit. For this process, an employable spinneret comprises a leading duct for a polyamide connected to an orifice via a vertical conduit, another leading duct for a polyurethane connected to an injection pipe obliquely extending therefrom, protruding into said conduit, opening immediately before said orifice and having a slit extending longitudinally at its under side along its entire protruded length.