PURPOSE: To relatively reduce measurement errors of the length of a lengthy material and to convey the lengthy material immediately after measurement.

CONSTITUTION: On a conveyance line for conveying a lengthy material to a working part 7, a stopper 43 is provided which can be brought into contact with one end of the lengthy material W, and the stopper 43 is constituted in capable of emerging in and out of the conveying level. Also, on the conveyance line, a carriage 49 is provided movable in the conveyance direction which can be brought into contact with the other end of the lengthy material W, and a position detecting device for detecting the position of the carriage 49 in the conveyance direction is provided. A calculating means is provided for calculating the length of the lengthy material W, when the stopper 43 is brought into contact with the lengthy material W and the carriage 49 is brought into contact with the other end of the lengthy material, based on the position of the carriage 49 in the conveyance direction detected by the position detecting device 57 and the position of the stopper 43 in the conveyance direction which is known from the beginning.