The employees were sent home from the Rocester site last Friday (August 28) when one of their colleagues tested positive for Covid-19.
They are expected to be able to return next Friday (September 11).
The affected employee works within the shop-floor quality area of the Backhoe Loader Division.
The news comes after 100 students from the neighbouring JCB Academy have also going into self-isolation after a coronavirus case at the school.
A JCB spokesman said: “An employee who works in the shop-floor quality area of the Backhoe Loader Division at JCB’s World HQ in Rocester last week tested positive for Covid-19.
“In line with company policy, when he developed symptoms, the employee remained at home and subsequently got tested.
“As a precaution, and in line with Public Health England guidelines, a deep clean of his working area was carried out and 20 colleagues who had come into contact with the employee were instructed to self-isolate for 14 days.
“None are displaying symptoms of Covid-19.”
All JCB employees affected will receive company sick pay ‘subject to qualifying service’.