To measure the traveling distance accurately regardless of abrasion of wheels by providing a touch roller touching the outer circumference of the wheels and detecting the r.p.m. of the touch roller thereby measure the traveling distance of a mobile.

A touch roller 1 touches the outer circumference of a fixed wheel 13 and a pulse encoder is combined to detect rotation of the rotary shaft of the touch roller 1 directly. In the case of a reach type forklift, a center of swing exists on the line connecting two fixed wheels 13 of an outrigger 12 during swing operation. Consequently, the fixed wheel 13 does not slide but rotate correctly. The touch roller 1 is touching the fixed wheel 13 while being urged constantly by a coil spring 5 so that the touch roller 1 does not slip. When a forklift travels, the fixed wheel 13 turns to cause rotation of the touch roller 1 and the r.p.m. thereof is detected by means of the pulse encoder thus detecting the traveling distance.