1. A parameter setting method of automatically generating a parameter used in a board inspecting process in a board inspecting apparatus which irradiates a mounted component on a board with a plurality of color rays at different incident angles and in order to define a boundary between a first part and a second part adjacent to the first part on the board in an image captured from their reflected lights, extracts a region that satisfies a predetermined color condition for defining a color having a tendency to appear in the first part, from the image and determines the boundary by comparing a feature of the extracted region with a predetermined determination condition, with steps comprising: capturing a plurality of teaching images by taking images of components; setting a plurality of patterns of color pickup regions each comprising a first region for picking up a color of the first part and a second region for picking up a color of the second part for each of the teaching images; mapping a color of each pixel in the first region and a color of each pixel in the second region as a target point and an exclusion point, respectively to a color space for each of the patterns of the color pickup regions; calculating a degree in separation between a target point distribution and an exclusion point distribution in the color space for each of the patterns of the color pickup regions; selecting a pattern of a color pickup region in which the degree in separation has a maximum value; finding a color range which divides the color space and has the largest difference between the number of target points and the number of exclusion points in the selected pattern; and setting the found color range as a color condition used for the board inspecting process.