PURPOSE: To execute the highly accurate weighing rapidly by providing a pair of shutters at the conveying path to the slave weigher and providing the control means to control to change the shutter weight in accordance with the weighing value.

CONSTITUTION: By the signal from a calculating control part 16 composed of a micro computer, etc., a master shutter driving part 11 to drive master shutters αa, αb, βa and βb is energized and the substance to be weighed is supplied to master pool hoppers 3a and 3b. Continuously, by the signal from the calculating control part 16, a master gate driving part 3' is energized, and when a master weigher 1 is alternately used, either of gates 31 and 32 of master pool hoppers 3a and 3b is opened, the substance to be weighed is supplied and weighed to the master weighing hopper and the weight is stored into the memory. Next, the weight from a slave weigher 2 is also stored to the memory, and the calculating control part 16 calculates the assembling target weight of the slave weigher 2 by the setting target weight set by a target weight setting part 18 and the weight from the master weigher 1, and executes the assembling calculation by the weight from the weigher 2.