A transmission for transmitting a motive power of an engine includes a counter shaft that receives a motive power from a crank shaft of an engine, a drive shaft that is connected to the crank shaft and configured to output the motive power, a multi-stage gear train that has a plurality of unit gear trains each having a drive gear and a driven gear, a plurality of jaw clutches each of which is movably provided between adjacent ones of the unit gear trains, a plurality of shift forks each of which is coupled to a corresponding one of the plurality of jaw clutches, and a shift cam that moves the plurality of jaw clutches via the plurality of shift forks to select one unit gear train in the multi-stage gear train that is to be used to transmit the motive power from the counter shaft to the drive shaft.