With the UN having faced criticism for an allegedly slow response to the virus, Ban started the tour in Liberia, the worst-hit country, after flying in from Ghana, where the UN Ebola mission is headquartered.
He later travelled to Sierra Leone and was due to fly to Guinea, the other two worst affected countries, as well as Mali. Mali has not seen a new case for three weeks, completing one of the two incubation periods the country needs to be declared free of the virus.
"The spread of the virus is slowing down in Liberia. Our response strategy is working."
He highlighted the international response and thanked health workers and military members who have travelled to the region to assist.
More From This Section
"We are committed to stand with you now as you face this merciless threat," Ban said.
"We will be with you until the outbreak is under control and the country has recovered.
Arriving later in Sierra Leone, Ban said efforts must be made to "get kids back in school, fields planted, and markets up and running again.
Ban's visit comes a year after the outbreak began in Guinea and follows sharp criticism from non-governmental organisations that UN agencies like the World Health Organization have been too slow to respond.
He was accompanied by Margaret Chan, head of the World Health Organization, David Nabarro, the UN coordinator for the fight against Ebola, and Anthony Banbury, the head of the UN Mission for Ebola Emergency Response or UNMEER.
It marked the highest-level such tour since the epidemic began. French President Francois Hollande had been the only non-African head of state to visit one of the worst-hit countries with is trip to Guinea on November 29.