The present invention relates to a process for preparing polyketone with improved catalytic activity and intrinsic viscosity, and specifically a process for preparing polyketone, in which as a catalyst component, an organometallic complex comprising palladium acetate, 1,3-bis[bis(2-methoxy-5-methylphenyl)phosphino]propane, and an anion of an acid with pKa of 4 or lower, as a liquid medium, a mixed solvent of methanol and 1000 to 10000 ppm of water, and upon polymerization, benzothiazole or benzophenone is added.