The firm is scheduled to shut the Pyeongtaek plant in the south of Seoul and shift its production line to the northern port city of Hải Phòng.
The company currently manufactures smartphones in the RoK, Việt Nam, Brazil and China while its domestic plants mostly produce premium devices.
LG Electronics has struggled in the smartphone market for years amid intense competition with Samsung and Apple in the hi-end segment and with Chinese manufacturers in the lower segment.
Last year, its sales of mobile devices hit US$1.5 billion but losses amounted to $280 million due to weak revenue and rising marketing costs.
Meanwhile, LG Display Co said Wednesday its net loss hit $55 million in the first quarter this year, higher than the $42.5 million in the same period last year due to low selling prices of liquid crystal displays.