A synchronization system includes a master unit and a slave unit. The slave unit is connected to the master unit directly, or indirectly via another slave unit, and is connected to at least one power supply device. The master unit transmits, to master downstream equipment, a first adjusted signal advanced in phase relative to a reference phase by a time corresponding to a time required to transmit a synchronization signal from the master unit to the master downstream equipment. The slave unit transmits, to slave downstream equipment, a second adjusted signal advanced in phase relative to a phase of the synchronization signal received from slave upstream equipment by a time corresponding to a sum of a time required to transmit the synchronization signal from the slave unit to the slave downstream equipment, and a processing time of the synchronization signal inside the slave unit.