1. An environment map generating apparatus comprising: a storage unit that stores a model of an obstacle; a cross-sectional image generating unit that generates a cross-sectional image of the model of the obstacle at a predetermined height from a reference plane in an environment; a model processing unit that generates a cross-sectional image-appended model by superimposing the cross-sectional image onto the model of the obstacle; an obtaining unit that obtains an obstacle map at the predetermined height from the reference plane in the environment; and an environment map generating unit that generates an environment map where the cross-sectional image-appended model is superimposed in a semitransparent state onto the corresponding obstacle in the obstacle map.