The baby was born to an infected mother at the Nongo Ebola treatment centre.
The last known Ebola patient in Guinea has recovered and been released from a treatment centre in the capital, Conakry, health officials say.
A spokesman for Guinea's Ebola co-ordination unit said two tests on the patient - a baby - had been negative.
Guinea will be declared officially free of Ebola if no new cases are reported in the next six weeks.
The epidemic, which began in Guinea, has killed more than 11,000 people in West Africa. Neighbouring Sierra Leone and Liberia have already been declared Ebola-free.
"The last confirmed case of Ebola has been released from a treatment centre," said Fode Tass Sylla of the Ebola co-ordination unit. "We did two tests after his treatment and they came back
The 19-day-old baby was born in the Nongo Ebola treatment centre but his infected mother did not survive, Reuters reported. Sierra Leone was declared Ebola-free by the World Health
Organization earlier this month after 42 days without a single declared case.
Liberia was declared free of the disease in September. The Ebola outbreak in West Africa was first reported in March 2014.