A drilling method and apparatus. A drilling device includes a plastic casing part and a drilling unit arranged essentially inside the casing part. The drilling unit includes a first drilling part for drilling a center hole and a second drilling part for reaming the center hole for the casing part. The drilling parts are arranged at a drilling head. The drilling parts are coupled in a power transmitting manner or in a radially contractable manner in connection with the casing part. A casing shoe is mounted at an end of the casing part. In coupling of the casing shoe at an end of the casing part, a casing shoe is used that includes a working member. The casing shoe is mounted at the end of the casing part by treating the casing part to provide a joint between the casting part and the casing shoe that transmits pulling.