To stably adjust tension of a belt without applying an excessive load on a tension roller pushing out the belt from the inside in a side conveyor.

Both top and bottom ends of a rotary shaft 13 of a tension roller 11 inside a conveying belt 3 are held by a support member 12. The support member is movable to a frame 5. A first deflection member is attached to an adjustment shaft 14 provided in the frame via a thread part, and a second deflection member fixed to the support member contacts the first deflection member on an inclined surface. If the first deflection member is raised by turning the adjustment shaft, the second deflection member is pushed up, so that the support member and the tension roller are moved to the outside. Further, the belt is pushed out to the outside to increase the tension. The tension decreases by turning the adjustment shaft reversely.