The baby was born in the Nongo Ebola treatment centre to an infected mother who did not survive.
Sixty-eight people who had been in contact with the country's last cluster of patients and were deemed at risk of developing the haemorrhagic fever were released from quarantine on Saturday.
A spokesman for Guinea's Ebola co-ordination unit said two tests on the patient - a baby - had been negative.
More than 11,000 people has killed in West Africa due to this epidemic, which began in Guinea,
Neighbouring Sierra Leone and Liberia have already been declared Ebola-free.
If no new cases are reported in the next six weeks then, Guinea will be declared officially free of Ebola.
By Ruchi Singh
