A wire reel containing portion (3) of a reinforcing bar binding machine (1) is provided with a rotation detecting lever (8) and a photosensor (7). When a wire reel is rotated in starting to bind a wire, rotation thereof is detected by the rotation detecting lever switched ON/OFF by a projected portion formed at a side face of the wire reel, the photosensor detects a reflection mark of the wire reel to determine a kind of the wire from a number of the marks, and a twist torque or the like is controlled. Wire information is detected not in an initializing operation (in setting wire) of rotating the wire reel at low speed but in a binding operation of rotating at high speed and therefore, an amount of swinging the rotation detecting lever is large and wire information can firmly be detected.