A positioning device for dental implant has a post and multiple guides. The post is cylindrical and has a diameter corresponding to a diameter of a hole in a dental model. The guides are mounted detachably on the post and are semi-tubular tabs and each has an inner concave, an inner diameter, and an outer diameter. The guides are mounted concentrically one another. A dentist can use the positioning device to precisely position a drill bit of a drilling device on an edentulous place of a patient's jaw bone and drills a bone cavity suitable for a dental implant. The drill bit can be easily inserted into the patient's mouth without opening excessively.