PURPOSE: To avoid generation of dangers due to erroneous operations in such a way that high speed rotation take-off condition and the low speed rotation take-off condition are positively shifted by shifting one piece of power take-off shaft in its shaft core direction.

CONSTITUTION: One piece of power take-off shaft 4 for a power take-off in a tractor is shifted by being reversed in the shaft core direction. A speed change gear 6 capable of shifting to high and low is constituted between the power take-off shaft 4 and a transmission shaft 5 laid in a transmission case 1, high speed rotation take-off condition and low speed rotation take-off condition can be shifted by reversing the shaft 4 for shifting. In consequence, discrimination of speed change condition from the outside can be easily made by the difference of configuration in the both end parts of the power take-off shaft without fear of any erroneous operation.