PURPOSE: To obtain a process for producing a high-mol.-wt. polyketone from carbon monoxide, a low-cost material, using a small amt. of a catalyst.

CONSTITUTION: In the process for producing a polyketone by copolymerizing carbon monoxide with an ethylenically unsatd. compd. in the presence of a catalyst, the catalyst used comprises a transition metal compd. having an atom selected from among atoms of the groups 10 and 11, a ligand having an atom of the group 15, and an oxide or heteropolyacid of phosphorus.