A combination weighing apparatus includes a dispersion unit, conveying units and weighing units. The dispersion unit is arranged to radially disperse product material. The conveying units are arranged around a periphery of the dispersion unit. The weighing units are arranged around a periphery of the conveying units. Each of the conveying units includes a trough. At least one of the troughs has a cross-sectional diameter that gradually increases generally from the inside end to the outside end so that the one of the troughs and an adjacent one of the troughs are kept in contact with each other from the inside ends to the outside ends. At least one of the conveying units has a spiral member disposed over a bottom surface of the trough. The spiral member is configured and arranged to convey the product material supplied from the dispersion unit toward the outside end of the trough.