A quick-release bit adapter includes a body having a driving hole extending from a driving section towards a connecting section of the body. The driving section includes a sliding hole extending at a non-parallel angle to and in communication with the driving hole. A resilient positioning member is mounted in the driving section. A releasing device is slideably mounted in the sliding hole. When the releasing device is in a first position, the resilient positioning member is engaged in cuts in an outer periphery of a bit in an engagement position received in the driving hole. When the releasing device is moved to a second position, the bit is disengaged from the resilient positioning member to allow easy removal of the bit.