To optimally arrange roofing material integrated solar battery modules having a rectangular form and same size on a roof setting surface, an arrangement range in which the solar battery modules can be arranged on the roof setting surface is determined. An arranging direction of the solar battery modules is determined. The number of solar battery modules which can be arranged almost horizontally in a line in the determined arranging direction and within the arrangement range is calculated. Solar battery modules of a line in a number not more than the calculated number are combined to form a solar battery module group. The solar battery module groups are arranged to set a center of the solar battery module group within the determined arrangement range and near a line almost vertically dividing the surface into two parts. The above operations are repeated a number of times corresponding to the number of lines of solar battery module groups which can be vertically arranged in the determined arranging direction and within the arrangement range.