The company has hired 50 employees for the operation of the unit and has lifted the total headcount of the factory to 480, the president's office said in a statement on Wednesday.
Gruner intends to open additional 50 jobs at the unit, which has a footprint of 3,000 square metres, by 2020, the president's office said.
The unit was officially opened on Wednesday in the presence of Serbian president Aleksandar Vucic.
Gruner launched its factory in Vlasotince in 2013. After the opening of the new unit, the factory covers 7,000 square metres.
The company produces relays, customised solenoids and actuators. In addition to Serbia, it also operates factories in Germany, Tunisia and India.