Colonel Doumbouya, 43, has ruled Guinea since overthrowing the country's first democratically elected president, Alpha Conde, in September 2021.
Conde had selected Doumbouya to lead the country's special forces group, which was supposed to protect the head of state from coups.
The September 2021 coup is among a string of putsches in West Africa since 2020, including in Mali, Burkina Faso and Niger.
Doumbouya was sworn in as president for a so-called transitional period, during which the junta said it intended to carry out far-reaching reforms in Guinea, which remains poor despite considerable natural resources.
Doumbouya on Tuesday hosted all Guinea's military units including more than 450 members of the Defence and Security Forces, the presidency posted on X, formerly Twitter.
It added that all the Defence and Security Forces expressed their desire to see the head of state elevated to the rank of general.
After initially declining "in his usual humility," Doumbouya accepted the position, it said.
Doumbouya also announced that he was stepping down as commander of the special forces group and would be replaced by his deputy, according to the presidency.
Under international pressure, the junta has promised to hand the reins of government back to elected civilians within two years, but the opposition has accused it of authoritarian drift.
Guinea Leader Doumbouya Promoted from Colonel to General
FILE - Guinea's junta leader Col. Mamady Doumbouya salutes during an independence day military parade in Bamako, Mali Thursday, Sept. 22, 2022
CONAKRY — The head of Guinea's ruling junta, Colonel Mamady Doumbouya, has been elevated to the rank of general, the presidency said on social media.