An opening device for a sealed package containing pourable product defines an axis and includes a frame fittable about a pierceable portion of the package and defining a pour opening coaxial with axis; a cap coaxially fitted onto the frame to close the pour opening; a tubular cutter engaging the pour opening coaxially with axis and movable relative to the frame to cut the pierceable portion; and a cutter protruding from one axial end of the cutter and cooperable with the pierceable portion to unseal the package; the cutter including at least one tooth having first and second cutting faces extending transversally to axis; the tooth also including one third cutting face between the first and second cutting faces and extending transversally to the first and second cutting faces; a first edge between the third and first cutting faces; and a second edge between the third and second cutting faces.