Polymerization catalysts for polyesters include: (1) metal elements selected from metal elements of Group 4A of the Periodic Table; and (2) metal elements selected from metal elements of Group 2A of the Periodic Table, aluminum, manganese, iron, cobalt, zinc, gallium and germanium. The catalysts are in a liquid state with a turbidity of at most 20% in a light path length of 10 mm, and a ratio the total amount of metal atoms derived from the above metal element (2) to the total amount of metal atoms derived from the above metal element (1) is from 0.50 to 3.50.