A process for producing cork lines which comprises holding a leader or leaders with a pair of metal molds having at the junctional surfaces thereof one or more cavities for forming a float or floats and one or more furrows formed so as to pass through said cavity or cavities for holding said leader or leaders, injecting a molten synthetic resin mixed with a foaming agent into said cavity or cavities to effect molding and foaming of said resin, cooling said metal molds and taking out a float or floats integrally fixed to said leader or leaders from said metal molds. An apparatus for producing cork lines which comprises an injection molding machine having a pair of metal molds with a cavity or cavities to form a float or floats and with furrows formed so as to pass through said cavity or cavities for holding a leader or leaders on the junctional surfaces of said metal molds, a device for maintaining said leader or leaders in stretched state between said metal molds and a device for intermittently conveying said leader or leaders in stretched state for a given distance in the longitudinal direction. A cork line thus produced can be used in various fields of industry, especially for fisheries.