An angle head holder is installed on a spindle having a positioning block mounted on its outer surface with a constraining groove. The angle head holder includes a body base, a driving shaft, a holder assembly, and a positioning device. The driving shaft and the holder assembly are disposed in the body base. The positioning device has a fixing ring and an adjusting assembly. The fixing ring is sleeved on the body base and has a receiving slot. The adjusting assembly has a connecting block, a positioning pin, and at least one lever pin. The connecting block is mounted to the fixing ring and has a receiving groove. The positioning pin protrudes out of the receiving groove, is limited by the constraining groove, and has a retaining groove. The at least one lever pin is mounted in the receiving slot and the retaining groove.