A semiconductor device includes a data obtaining unit that obtains a plurality of data items each indicating a result of observation from a plurality of radars for observing surroundings, converts the plurality of data items into data items in a polar coordinate format, and stores them in a storage unit, an axial position converting unit that performs conversion on the plurality of data items in the polar coordinate data format stored in the storage unit so that their axial positions will be the same, generates the plurality of data items on which axial position conversion has been performed, and stores them in the storage unit, a data superimposing unit that superimposes the plurality of data items on which the axial position conversion has been performed to generate superimposed data, and a coordinate converting unit that converts the superimposed data into data in a Cartesian coordinate format.