A ratchet driving tool includes a driving shank secured to a base supporting element and having two non-circular engaging segments, a casing engaged onto the driving shank and the engaging segments and having a groove and a slot for engaging with engaging elements, two gears engaged onto the casing and around the engaging elements for allowing the engaging elements to be engaged between the gears and the engaging segments and for determining a driving direction of the driving shank by the casing and the gears, a housing is attached to the base supporting element, and a control ferrule is engaged with the one of the gears for rotating the gears and the driving shank with the engaging elements.