thermal stability can be declined in process and if content of water is more than 10 part by weight mechanical properties of product can be declined when the polyketone of the present invention is polymerized benzophenone may be added as needed by adding benzophenone the effect of improving the intrinsic viscosity of the polyketone can be achieved an amount of benzophenone added is such that a molar ratio of a the ninth tenth or eleventh transition metal compound to benzophenone is maintained at 1 5 100 preferably 1 40 60 if the molar ratio of the transition metal to the benzophenone is less than 1 5 effect of improving the intrinsic viscosity of the produced polyketone is unsatisfactory if the molar ratio of the transition metal to the benzophenone is more than 1 100 the polyketone catalytic convergence is rather reduced an amount of a the group 9 group 10 or group 11 transition metal compound used varies depending on a kind of an ethylenically unsaturated compound selected and other polymerization conditions but is usually 0 01 to 100 mol preferably 0 01 to 10 mol per liter of capacity of reaction zone the capacity of the reaction zone refers to liquid phase capacity of a reactor an amount of the ligand b used is not particularly limited but is usually.