The present invention provides an obstacle avoiding apparatus, an obstacle avoiding method, an obstacle avoiding program, and a mobile robot apparatus that can accurately model a robot apparatus and plan a highly precise moving route for the robot apparatus that avoids obstacles. The obstacle avoiding apparatus, to be used for a mobile robot apparatus to avoid obstacles, includes an obstacle environment map drawing section that divides the range of height from the reference surface for the mobile robot apparatus to move thereon to the height of the mobile robot apparatus into a plurality of layers corresponding to predetermined respective ranges of height and draws obstacle environment maps, each showing the condition of being occupied by one or more than one obstacles existing in the corresponding layer, and a route planning section that plans a route for the robot apparatus to move along according to an enlarged environment map prepared by enlarging the area occupied by the obstacle or obstacles in the obstacle environment maps as a function of the cross sectional profile of the mobile robot apparatus in each of the layers.