The invention discloses a tree excavating machine. The technical scheme is characterized in that the tree excavating machine comprises a vehicle body, a tree excavating device is arranged at the front end of the vehicle body and connected on the vehicle body in a manner of sliding up and down, a first oil cylinder for driving the tree excavating device to slide is arranged on the vehicle body, the tree excavating device comprises a main arm fixedly connected on the first oil cylinder, a rotating shaft arranged along the vertical direction is arranged on the main arm, an auxiliary arm sleeves the rotating shaft and is connected on the same in a manner of rotating along the axis direction of the rotating shaft, a plurality of blades sliding up and down are arranged on the auxiliary arm and encircle and wrap root systems and soil blocks of a tree, a support for abutting against the ground is arranged on the auxiliary arm, connected on the auxiliary arm in a manner of sliding up and down and positioned on one side, close to the ground, of the auxiliary arm. By arranging the support sliding up and down, the tree excavating machine can excavate the soil blocks different in size, so that using range of the tree excavating machine is widened.