The resent invention relates to a driving assisting device for a wheelchair on a slope, which is installed between a hand rim and a rear wheel of a wheelchair. The purpose of the present invention is to provide the driving assisting device for a wheelchair on the slope, which can be automatically changed to a state suitable to driving on an uphill road and a downhill road in accordance with an inclination of a road. The driving assisting device for a wheelchair on the slope includes: a gearshift including an input shaft connected to the hand rim to move forward and backward, and a first input gear and a second input gear, which are an input gear installed at an end of the input shaft and have different numbers of teeth at a first reduction gear ratio and a second reduction gear ratio； a first driven gear selectively engaged to one among the first input gear or the second input gear of the gearshift； a second driven gear engaged with the first driven gear at normal times； an internal gear engaged to the second driven gear at the normal times and connected to transfer power to the rear wheel； a weight installed to rotate； and a wire for speed change installed to be eccentric to a rotation center of the weight and connected to the input shaft to move the input shaft forward or backward by corresponding to an angle change of the weight on the driving assisting device for a wheelchair on the slope in order for one with a higher reduction gear ratio among the first input gear and the second input gear to be engaged with the first driven gear when the wheelchair is on the uphill road. A weight device includes a latchet gear rotating only in a direction in which the wheelchair moves forward. When the wheelchair is on the uphill road, the latchet gear is engaged with the first driven gear by corresponding to the angle change of the weight on the driving assisting device for a wheelchair on the slope. The input gear is formed in a cone shape in which the diameter of an input
