In a walk behind lawnmower 1 for mowing lawns that bifurcates a power from an engine 5 and transmits it to drum-type wheels 7L, 7R and a reel cutter 12, each of the first power transmission passage 35 for transmitting the power from the engine 5 to the drum-type wheels 7L, 7R and the second power transmission passage 36 for transmitting the power from the engine 5 to the reel cutter 12 has a gear variable speed mechanism 30 and an interchange mechanism 134 as speed changing structures for changing a rotating speed of each of drum shafts 16L, 16R as driving shafts.
