Conveyance system, main dolly, and maintenance method for semiconductor production apparatus

A maintenance method for a semiconductor production apparatus comprising:

• using a conveyance system including a main dolly that includes a cargo platform, three or more wheels supporting the cargo platform, and a handle connected to the cargo platform, and a sub dolly that is configured to be movable between a position on the cargo platform of the main dolly and a position outside the cargo platform, the sub dolly including a front wheel and a rear wheel enabling the sub dolly to move at least in a forward and backward direction, a holder configured to hold an object so that its center of gravity is located ahead of the front wheel, and a counterweight detachably provided behind the front wheel, the main dolly being configured to be capable of carrying and conveying the sub dolly in a state of holding the object, to cause the sub dolly to hold the object in the semiconductor production apparatus, carrying the sub dolly in a state of holding the object on the main dolly, and carrying out the sub dolly from the semiconductor production apparatus;
• and
• carrying the sub dolly in a state of holding a replacement object on the main dolly and carrying the sub dolly into the semiconductor production apparatus, and disposing the replacement object held by the sub dolly inside the semiconductor production apparatus.