We theoretically studied reaction paths of Wohler's urea synthesis using the artificial force induced reaction method and the rate constant matrix contraction method. The systematic search resulted in a reaction path network consisting of 885 local minima. The network includes not only paths giving the main product, urea, but also those leading to a byproduct, carbonic acid. The reaction path network thus provided an entire picture of the mechanism of Wohler's urea synthesis including the reaction selectivity.