One of the two production lines at the factory was restarted on Wednesday, Toshiba Electronic Devices & Storage Corp said in a statement. It did not say when the other line would reopen.
The plant makes system LSI chips, around 60% of which are sold to automakers and industrial machinery makers.
The company also makes those chips at a factory in northern Japan, with other domestic producers, such as Renesas Electronics Corp, also building the devices.
(Reporting by Tim Kelly; Editing by Christopher Cushing)