To avoid the damage of the groove depth detector caused by contact with other grounding bodies.

This rice transplanter is equipped with an automatic lift controller 26B which automatically controls the lifting and lowering of the transplanting unit 5 to the running machine body 1 based on the detection information from the float sensor 28 which detects the displacement magnitude in the vertical vibration of the land-leveling float 17 and with an automatic sensor adjuster 26D which automatically adjusts the sensitivity of the float sensor 28 based on the detection information from the groove depth-detecting sensor A detecting the depth of the grooves formed after the float 17 passes the mud surface of the rice paddies, which is caused by deviation in the grounding level of the grounding bodies 33, 34 contacting with the mud surface at the rear of the leveling float 17. At this time, an attitude-switching means B is mounted to switch the posture between the action mode where the grounding bodies 33, 34 of the groove depth detector A ground to the mud face and the non-action mode where the bodies part away from the mud face.