A system for performing an operation for a circuit substrate, including a plurality of main conveyors each of which conveys, positions, and supports a circuit substrate, the plurality of main conveyors being arranged in a direction perpendicular to a circuit-substrate conveying direction in which the each main conveyor conveys the circuit substrate, an operation performing device which performs at least one operation for the circuit substrate positioned and supported by the each main conveyor, at least one of (a) a carry-in conveyor which conveys the circuit substrate to the each main conveyor and loads the circuit substrate thereon, and (b) a carry-out conveyor which loads the circuit substrate off the each main conveyor and conveys the circuit substrate away therefrom, and a conveyor shifting device which selectively shifts the at least one of the carry-in conveyor and the carry-out conveyor to one of a plurality of shift positions at each of which the one conveyor is aligned with a corresponding one of the main conveyors.