A nail tip guide tool is attached to an end of a nose of a nailing machine to provide guide pieces on a bottom surface inside same, the nail guide tool having a lower portion in a funnel shape. The top surfaces of the guide pieces have a recess in a mortar shape when brought together at the center of the funnel shape by a press board member biased by a coil spring. The guide pieces are used so that in the nose, the tip of a nail in an inclined posture is guided to a center of the mortar shape and is inserted thereamong, and correcting the posture thereof. For fastening a metal piece with a nail, distal ends of the guide pieces are structured to form a conical shape, and with this portion having been fitted into a pilot hole of the metal piece, the nail is struck.