The aim of the present invention is to ensure the existing arbitrary step-down operation device to be used for lifting operation part so as to implement dual purpose. The present invention relates to an agricultural operation machine, installing an operation part on running body by means of lifting coupling rod mechanism, setting operation part lifting freely using fluidic pressure lifting tank, and controlling the operation part with a prescribed height relative to ground based on detecting result of a ground sensor setting on the operation part. The agricultural operation machine also includes a lifting operation device for lifting the operation part to non-operation position, a step-down operation device for decreasing the operation part to a earth-contact position, an arbitrary operation device for lifting or decreasing the operation part, a drive switching device for transferring the operation part to drive state and non-drive state, a control device for descreasing the operationpart only during the operation period of the arbitrary operation device when the operation part lies in non-drive state, and lifting the operation part only during the operation period of the arbitrary operation device when the operation part lies in drive state.
