PURPOSE: To saw continuously supplied lumber automatically with high yield and high quality by turning lumber to be placed in the most suitable position for conversion, controlling the movement of lumber in its upper and lower, and right and left sides, and grasping the lumber core in its cut end to be supplied in a longitudinal direction approximately horizontally.

CONSTITUTION: At first, one piece of a number of lumber 1 being arranged directionally is taken out, and the diameter of the butt end and the distal end is measured by first measuring means 10 so as to obtain a lumber core that connects the center between the butt end and the distal end. Subsequently, by operating lumber core correction means 16 on the basis of the lumber core for bearing both the cut ends of lumber 1 to be held in a freely turning manner, and by placing a second measuring means 58 composed of a plurality of parts at intervals correspondingly for measuring respective turning diameters in order to measure the lumber diameter and straightness such as the curvature thereof. Then, lumber 1 is turned to be placed in the most suitable position for log bucking, and moved in the upper and lower, and right and left direction to be adjusted with respect to the sawing path and then carried in along the conveying path (s), and thereafter it is grasped in its lumber core and supplied to the lumber sawing machine B for lumbering.