The declaration came as the World Health Organization reported the death toll from the Ebola outbreak in West Africa had reached 1,069, including 377 in Guinea.
WHO has recorded a total of 510 cases in Guinea since the outbreak began in February.
The other cases were reported in Liberia, Sierra Leone and Nigeria. All four countries have now declared national health emergencies in response to the outbreak.
With the declaration of a health emergency, Guinea's state radio reported that border controls will tighten, those suspected of having Ebola will be isolated and corpses will be prohibited from transportation between towns.
Those who fail to follow Guinea's Ebola response procedures will, the president reportedly said, be considered "a threat to public health and will face the might of the law."