A method for generating at least one image data set for training to be used for a CNN capable of detecting objects in an input image is provided for improving hazard detection while driving. The method includes steps of: a computing device (a) acquiring a first label image in which edge parts are set on boundaries between the objects and a background and different label values are assigned corresponding to the objects and the background; (b) generating an edge image by extracting edge parts from the first label image; (c) generating a second label image by merging the first label image with a reinforced edge image, generated by assigning weights to the extracted edge parts; and (d) storing the input image and the second label image as the image data set. Further, the method allows a degree of detecting traffic sign, landmark, road marker and the like to be increased.